soc/amd/cezanne: Add uart.c to smm so we can support DEBUG_SMI

Signed-off-by: Raul E Rangel <rrangel@chromium.org>
Change-Id: Ife43352db564654ed538383a157431ee10856518
Reviewed-on: https://review.coreboot.org/c/coreboot/+/50617
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Felix Held <felix-coreboot@felixheld.de>

src/soc/amd/cezanne/Makefile.inc

@@ -37,6 +37,7 @@ ramstage-y	+= root_complex.c
 ramstage-y	+= uart.c
 
 smm-y		+= smihandler.c
+smm-$(CONFIG_DEBUG_SMI) += uart.c
 
 CPPFLAGS_common += -I$(src)/soc/amd/cezanne/include
 CPPFLAGS_common += -I$(src)/soc/amd/cezanne/acpi