arch/x86: Use wildcard for mb/smihandler.c

Change-Id: I306f8cd74af62c0cd30f445d20c47f774f122481
Signed-off-by: Kyösti Mälkki <kyosti.malkki@gmail.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/49247
Reviewed-by: Angel Pons <th3fanbus@gmail.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

src/arch/x86/Makefile.inc

@@ -294,6 +294,4 @@ smm-y += memmove.c
 smm-y += memset.c
 smm-$(CONFIG_X86_TOP4G_BOOTMEDIA_MAP) += mmap_boot.c
 
-ifneq ($(wildcard src/mainboard/$(MAINBOARDDIR)/smihandler.c),)
-smm-srcs += src/mainboard/$(MAINBOARDDIR)/smihandler.c
-endif
+smm-srcs += $(wildcard src/mainboard/$(MAINBOARDDIR)/smihandler.c)