soc/amd: move assembly part of non-CAR bootblock to common directory

There will be more files added to the common non-CAR Makefile.inc, so
use an ifeq statement there.

Change-Id: I1f71954d27fbf10725387a0e95bc57f5040024cc
Signed-off-by: Felix Held <felix-coreboot@felixheld.de>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/47880
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Martin Roth <martinroth@google.com>

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

@@ -1 +1,2 @@
 subdirs-$(CONFIG_SOC_AMD_COMMON_BLOCK_CAR) += car
+subdirs-$(CONFIG_SOC_AMD_COMMON_BLOCK_NONCAR) += noncar

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

@@ -0,0 +1 @@
+bootblock-y += pre_c.S

src/soc/amd/picasso/Makefile.inc

@@ -11,7 +11,6 @@ subdirs-y += ../../../cpu/x86/pae
 subdirs-y += ../../../cpu/x86/smm
 subdirs-$(CONFIG_VBOOT_STARTS_BEFORE_BOOTBLOCK) += psp_verstage
 
-bootblock-y += bootblock/pre_c.S
 bootblock-y += bootblock/bootblock.c
 bootblock-y += aoac.c
 bootblock-y += southbridge.c