cmsisDAP: Avoid memcpy() on possibly overlapping buffer

I observed strange cmsisDAP behavior when building openFPGALoader with
Clang/musl in release mode: CmsisDAP:display_info() shows the correct
hardware capability that supports JTAG,

	...
	firmware version : 0254
	hardware capabilities : 13
	SWO trace buffer size : NA
	...

but the detection of JTAG fails in the constructor with a strange
response sequence,

	Hardware cap 00 01 00
	JTAG init failed with: JTAG is not supported by the probe

With some digging, it's found that the CmsisDAP::xfer() method without
an instruction parameter may be called by the constructor with a rx_buff
pointer overlapping with _ll_buffer, for which memmove() instead of
memcpy() should be used. The behavior of memcpy() is undefined when dst
and src overlap.

Fixes: 53c5d35 ("add cmsis dap (hid) support")
Signed-off-by: Yao Zi <[email protected]>

Author: ziyao233

src/cmsisDAP.cpp

@@ -561,7 +561,7 @@ int CmsisDAP::xfer(int tx_len, uint8_t *rx_buff, int rx_len)
 		return ret;
 	}
 	if (rx_len)
-		memcpy(rx_buff, _ll_buffer, rx_len);
+		memmove(rx_buff, _ll_buffer, rx_len);
 
 
 	return ret;