Fix TypeError where address_offset and base_address are treated as strings

This happened for example for the rp2040 pac:

```
$ svd patch svd/rp2040.yaml
Traceback (most recent call last):
  File "/home/jan/.local/bin/svd", line 10, in <module>
    sys.exit(svdtools_cli())
  File "/home/jan/.local/lib/python3.7/site-packages/click/core.py", line 1130, in __call__
    return self.main(*args, **kwargs)
  File "/home/jan/.local/lib/python3.7/site-packages/click/core.py", line 1055, in main
    rv = self.invoke(ctx)
  File "/home/jan/.local/lib/python3.7/site-packages/click/core.py", line 1657, in invoke
    return _process_result(sub_ctx.command.invoke(sub_ctx))
  File "/home/jan/.local/lib/python3.7/site-packages/click/core.py", line 1404, in invoke
    return ctx.invoke(self.callback, **ctx.params)
  File "/home/jan/.local/lib/python3.7/site-packages/click/core.py", line 760, in invoke
    return __callback(*args, **kwargs)
  File "/home/jan/.local/lib/python3.7/site-packages/svdtools/cli.py", line 16, in patch
    svdtools.patch.main(yaml_file)
  File "/home/jan/.local/lib/python3.7/site-packages/svdtools/patch.py", line 1639, in main
    process_device(svd, root)
  File "/home/jan/.local/lib/python3.7/site-packages/svdtools/patch.py", line 1616, in process_device
    d.process_peripheral(periphspec, device[periphspec], update_fields)
  File "/home/jan/.local/lib/python3.7/site-packages/svdtools/patch.py", line 717, in process_peripheral
    p.derive_register(rname, rderive)
  File "/home/jan/.local/lib/python3.7/site-packages/svdtools/patch.py", line 865, in derive_register
    ET.SubElement(rtag, "addressOffset").text = address_offset
  File "src/lxml/etree.pyx", line 1041, in lxml.etree._Element.text.__set__
  File "src/lxml/apihelpers.pxi", line 748, in lxml.etree._setNodeText
  File "src/lxml/apihelpers.pxi", line 736, in lxml.etree._createTextNode
  File "src/lxml/apihelpers.pxi", line 1539, in lxml.etree._utf8
TypeError: Argument must be bytes or unicode, got 'int'
```

To fix that error, convert the addresses to hex strings explicitly.

Author: jannic

svdtools/patch.py

@@ -530,14 +530,14 @@ def derive_peripheral(self, pname, pmod):
         if ptag is None:
             ptag = ET.SubElement(parent, "register")
             ET.SubElement(ptag, "name").text = pname
-            ET.SubElement(ptag, "addressOffset").text = base_address
+            ET.SubElement(ptag, "addressOffset").text = hex(base_address)
         else:
             for value in list(ptag):
                 if value.tag in ("name", "baseAddress", "interrupt", "description"):
                     continue
                 ptag.remove(value)
             if base_address:
-                ptag.find("baseAddress").text = base_address
+                ptag.find("baseAddress").text = hex(base_address)
             if description:
                 ptag.find("description").text = description
         for value in ptag:
@@ -862,14 +862,14 @@ def derive_register(self, rname, rmod):
         if rtag is None:
             rtag = ET.SubElement(parent, "register")
             ET.SubElement(rtag, "name").text = rname
-            ET.SubElement(rtag, "addressOffset").text = address_offset
+            ET.SubElement(rtag, "addressOffset").text = hex(address_offset)
         else:
             for value in list(rtag):
                 if value.tag in ("name", "addressOffset", "description"):
                     continue
                 rtag.remove(value)
             if address_offset:
-                rtag.find("addressOffset").text = address_offset
+                rtag.find("addressOffset").text = hex(address_offset)
             if description:
                 rtag.find("description").text = description
         for value in rtag: