soc/amd/genoa_poc: Allow using UART with DEBUG_SMI=y

When DEBUG_SMI is selected, common code may use these helpers to handle
addressing and initialising the SoC-specific UART. Therefore, add uart.c
to be compiled into SMM.

Change-Id: If7c6f2346d5f9ffb371d51d1de6f0b695acedf10
Signed-off-by: Benjamin Doron <benjamin.doron@9elements.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/81072
Reviewed-by: Marvin Drees <marvin.drees@9elements.com>
Reviewed-by: Felix Held <felix-coreboot@felixheld.de>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Lean Sheng Tan <sheng.tan@9elements.com>
Reviewed-by: Angel Pons <th3fanbus@gmail.com>

src/soc/amd/genoa_poc/Makefile.mk

@@ -22,6 +22,7 @@ ramstage-y	+= smihandler.c
 ramstage-y	+= mca.c
 
 smm-y		+= smihandler.c
+smm-$(CONFIG_DEBUG_SMI) += uart.c
 
 CPPFLAGS_common += -I$(src)/soc/amd/genoa_poc/acpi
 CPPFLAGS_common += -I$(src)/soc/amd/genoa_poc/include