net: ethernet: bgmac: Remove -Warray-bounds exception

GCC-12 emits false positive -Warray-bounds warnings with
CONFIG_UBSAN_SHIFT (-fsanitize=shift). This is fixed in GCC 13[1],
and there is top-level Makefile logic to remove -Warray-bounds for
known-bad GCC versions staring with commit f0be87c4 ("gcc-12: disable
'-Warray-bounds' universally for now").

Remove the local work-around.

[1] https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105679



Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: David S. Miller <davem@davemloft.net>