soc/amd/common/block/cpu: move Makefile guards into subfolders

The next patch will add a tsc subfolder that might end up containing
code that is guarded with different Kconfig options, so move the guards
into the Makefiles in the subfolders instead of guarding the inclusion
of the Makefiles in the subdirectories with the corresponding Kconfig
option.

Change-Id: Iafc867eb9adcb23e9a4878cc381684db6f9692d5
Signed-off-by: Felix Held <felix-coreboot@felixheld.de>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/48312
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Marshall Dawson <marshalldawson3rd@gmail.com>

src/soc/amd/common/block/cpu/Makefile.inc

@@ -1,2 +1 @@
-subdirs-$(CONFIG_SOC_AMD_COMMON_BLOCK_CAR) += car
-subdirs-$(CONFIG_SOC_AMD_COMMON_BLOCK_NONCAR) += noncar
+subdirs-y += ./*

src/soc/amd/common/block/cpu/car/Makefile.inc

@@ -1,3 +1,5 @@
+ifeq ($(CONFIG_SOC_AMD_COMMON_BLOCK_CAR),y)
+
 bootblock-y += cache_as_ram.S
 bootblock-y += ap_exit_car.S
 bootblock-y += exit_car.S
@@ -6,3 +8,5 @@ postcar-y += exit_car.S
 
 romstage-y += ap_exit_car.S
 romstage-y += exit_car.S
+
+endif # CONFIG_SOC_AMD_COMMON_BLOCK_CAR

src/soc/amd/common/block/cpu/noncar/Makefile.inc

@@ -1 +1,5 @@
+ifeq ($(CONFIG_SOC_AMD_COMMON_BLOCK_NONCAR),y)
+
 bootblock-y += pre_c.S
+
+endif # CONFIG_SOC_AMD_COMMON_BLOCK_NONCAR