soc/amd/common/block/graphics: Use vbt_get()

Implement vbt_get() on AMD and return the VBIOS location. This allows
to drop the hardcoded addresses used in various places and return an
address in DRAM that is reserved for FSP use.

TEST: amd/birman+ still gets passed the correct VBIOS address.

Change-Id: I92d76fc4df88fbce792b9d7c912c6799617704a0
Signed-off-by: Patrick Rudolph <patrick.rudolph@9elements.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/86299
Reviewed-by: Jérémy Compostella <jeremy.compostella@intel.com>
Reviewed-by: Felix Held <felix-coreboot@felixheld.de>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Ana Carolina Cabral <ana.cpmelo95@gmail.com>

src/drivers/intel/fsp2_0/silicon_init.c

@@ -14,7 +14,12 @@
 #include <mrc_cache.h>
 #include <program_loading.h>
 #include <soc/intel/common/reset.h>
+#if CONFIG(SOC_AMD_COMMON)
+#include <amdblocks/vbt.h>
+#endif
+#if CONFIG(SOC_INTEL_COMMON)
 #include <soc/intel/common/vbt.h>
+#endif
 #include <stage_cache.h>
 #include <string.h>
 #include <timestamp.h>