soc/amd/phoenix: Remove non-functional APCB check

The way the PSP_APCB_FILES list is created will always insert at least a
space into it. When tested by the if, this space will prevent the else
clause from ever running and never generate a build error.

Remove the non-functional check. Instead, mainboards should select
warn_no_apcb or die_no_apcb to generate a warning message or build error
if the APCB is missing.

Signed-off-by: Fred Reitberger <reitbergerfred@gmail.com>
Change-Id: Ib9fe0f05739fb19da2494629dc1d5aaa0ca6431f
Reviewed-on: https://review.coreboot.org/c/coreboot/+/73006
Reviewed-by: Martin L Roth <gaumless@gmail.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

src/soc/amd/phoenix/Makefile.inc

@@ -239,7 +239,6 @@ $(obj)/amdfw.rom:	$(call strip_quotes, $(PSP_BIOSBIN_FILE)) \
 			$(AMDFWTOOL) \
 			$(obj)/fmap_config.h \
 			$(objcbfs)/bootblock.elf # this target also creates the .map file
-	$(if $(PSP_APCB_FILES), ,$(error APCB_SOURCES is not set))
 	rm -f $@
 	@printf "    AMDFWTOOL  $(subst $(obj)/,,$(@))\n"
 	$(AMDFWTOOL) \