kbuild: uapi: Strip comments before size type check

On m68k, check_sizetypes in headers_check reports:

    ./usr/include/asm/bootinfo-amiga.h:17: found __[us]{8,16,32,64} type without #include <linux/types.h>

This header file does not use any of the Linux-specific integer types,
but merely refers to them from comments, so this is a false positive.
As of commit c3a9d74e ("kbuild: uapi: upgrade check_sizetypes()
warning to error"), this check was promoted to an error, breaking m68k
all{mod,yes}config builds.

Fix this by stripping simple comments before looking for Linux-specific
integer types.

Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
Reviewed-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
Link: https://patch.msgid.link/949f096337e28d50510e970ae3ba3ec9c1342ec0.1759753998.git.geert@linux-m68k.org


[nathan: Adjust comment and remove unnecessary escaping from slashes in
         regex]
Signed-off-by: Nathan Chancellor <nathan@kernel.org>