net: ethernet: mediatek: 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 f0be87c42cbd ("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 <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

drivers/net/ethernet/mediatek/Makefile

···
 endif
 obj-$(CONFIG_NET_MEDIATEK_SOC_WED) += mtk_wed_ops.o
 obj-$(CONFIG_NET_MEDIATEK_STAR_EMAC) += mtk_star_emac.o
-
-# FIXME: temporarily silence -Warray-bounds on non W=1+ builds
-ifndef KBUILD_EXTRA_WARN
-CFLAGS_mtk_ppe.o += -Wno-array-bounds
-endif