staging: rtl8723au: Add compiler check for -Wtype-limits

Gcc versions before 4.3 do not support -Wtype-limits:

cc1: error: unrecognized command line option "-Wtype-limits"

Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
Acked-by: Jes Sorensen <Jes.Sorensen@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>