drm/msm: Fix gen_header.py for older python3 versions

The gen_header.py script is failing for older versions of python3 such
as python 3.5. Two issues observed with python 3.5 are ...

 1. Python 3 versions prior to 3.6 do not support the f-string format.
 2. Early python 3 versions do not support the 'required' argument for
    the argparse add_subparsers().

Fix both of the above so that older versions of python 3 still work.

Fixes: 8f7abf0 ("drm/msm: generate headers on the fly")
Signed-off-by: Jon Hunter <[email protected]>
Reviewed-by: Dmitry Baryshkov <[email protected]>
Patchwork: https://patchwork.freedesktop.org/patch/589427/
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Dmitry Baryshkov <[email protected]>

Author: jonhunter

drivers/gpu/drm/msm/registers/gen_header.py

@@ -323,7 +323,7 @@ def indices(self):
 			indices = []
 		if self.length != 1:
 			if self.fixed_offsets:
-				indices.append((self.index_ctype(), None, f"__offset_{self.local_name}"))
+				indices.append((self.index_ctype(), None, "__offset_%s" % self.local_name))
 			else:
 				indices.append((self.index_ctype(), self.stride, None))
 		return indices
@@ -942,7 +942,8 @@ def main():
 	parser.add_argument('--rnn', type=str, required=True)
 	parser.add_argument('--xml', type=str, required=True)
 
-	subparsers = parser.add_subparsers(required=True)
+	subparsers = parser.add_subparsers()
+	subparsers.required = True
 
 	parser_c_defines = subparsers.add_parser('c-defines')
 	parser_c_defines.set_defaults(func=dump_c_defines)