HID: microsoft: do not use compound literal - fix build

In patch "HID: microsoft: fix invalid rdesc for 3k kbd" I fixed
support for MS 3k keyboards. However the added check using memcmp and
a compound statement breaks build on architectures where memcmp is a
macro with parameters.

hid-microsoft.c:51:18: error: macro "memcmp" passed 6 arguments, but takes just 3

On x86_64, memcmp is a function, so I did not see the error.

Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Reported-by: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>