soc/amd/common: introduce SOC_AMD_COMMON_BLOCK_PCI_MMCONF

Add a Kconfig symbol for including the PCIe MMCONF setup function in the
build and select it when SOC_AMD_COMMON_BLOCK_PCI is selected and in the
southbridges call enable_pci_mmconf(), but don't select
SOC_AMD_COMMON_BLOCK_PCI.

Change-Id: I32de7450bff5b231442f9f2094a18ebe01874ee7
Signed-off-by: Felix Held <felix-coreboot@felixheld.de>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/47878
Reviewed-by: Martin Roth <martinroth@google.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
diff --git a/src/southbridge/amd/cimx/sb800/Kconfig b/src/southbridge/amd/cimx/sb800/Kconfig
index 96737cf..ecfc1e1 100644
--- a/src/southbridge/amd/cimx/sb800/Kconfig
+++ b/src/southbridge/amd/cimx/sb800/Kconfig
@@ -10,6 +10,7 @@
 	select HAVE_CF9_RESET_PREPARE
 	select SOC_AMD_COMMON
 	select SOC_AMD_COMMON_BLOCK_ACPIMMIO
+	select SOC_AMD_COMMON_BLOCK_PCI_MMCONF
 
 if SOUTHBRIDGE_AMD_CIMX_SB800
 config ENABLE_IDE_COMBINED_MODE