soc/amd/{CZN,MDN,PCO}: Fix building with only single RW region

apu/amdfw_a was only getting added to CBFS when VBOOT_SLOTS_RW_AB was
selected, but needs to be added in the RW_A only case as well
(VBOOT_SLOTS_RW_A). Since VBOOT_SLOTS_RW_AB selects VBOOT_SLOTS_RW_A,
we can guard amdfw_a and _b separately and both will be added in the
RW_AB case.

TEST=build google/zork with VBOOT_SLOTS_RW_A or VBOOT_SLOTS_RW_AB
selected, ensure amdfw_a and amdfw_b are added to correct CBFS regions
as appropriate.

Change-Id: Ic8048e869d7449eeb1ac10bfec4a5646b848d6a8
Signed-off-by: Matt DeVillier <matt.devillier@amd.corp-partner.google.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/68126
Reviewed-by: Fred Reitberger <reitbergerfred@gmail.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Raul Rangel <rrangel@chromium.org>
diff --git a/src/soc/amd/cezanne/Kconfig b/src/soc/amd/cezanne/Kconfig
index 43c83bf..35b9215 100644
--- a/src/soc/amd/cezanne/Kconfig
+++ b/src/soc/amd/cezanne/Kconfig
@@ -484,7 +484,7 @@
 	  This is the byte before the default first byte used by VBNV
 	  (0x26 + 0x0E - 1)
 
-if VBOOT_SLOTS_RW_AB && VBOOT_STARTS_BEFORE_BOOTBLOCK
+if VBOOT_SLOTS_RW_A && VBOOT_STARTS_BEFORE_BOOTBLOCK
 
 config RWA_REGION_ONLY
 	string
@@ -493,6 +493,10 @@
 	  Add a space-delimited list of filenames that should only be in the
 	  RW-A section.
 
+endif # VBOOT_SLOTS_RW_A && VBOOT_STARTS_BEFORE_BOOTBLOCK
+
+if VBOOT_SLOTS_RW_AB && VBOOT_STARTS_BEFORE_BOOTBLOCK
+
 config RWB_REGION_ONLY
 	string
 	default "apu/amdfw_b"