soc/amd/cezanne: Add pre-FSPM call to the mainboard

The Guybrush platform needs to set up some GPIOs immediately before the
FSP-M runs.  Add a platform specific call.  This will be used in a
follow-on commit.

BUG=b:184796302, b:184598323
TEST=Build

Signed-off-by: Martin Roth <martinroth@chromium.org>
Change-Id: I37d2625ff426347852e98a9a50f15368e0213449
Reviewed-on: https://review.coreboot.org/c/coreboot/+/54638
Reviewed-by: Felix Held <felix-coreboot@felixheld.de>
Reviewed-by: Marshall Dawson <marshalldawson3rd@gmail.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
diff --git a/src/soc/amd/cezanne/fsp_m_params.c b/src/soc/amd/cezanne/fsp_m_params.c
index 352aeef..9546721 100644
--- a/src/soc/amd/cezanne/fsp_m_params.c
+++ b/src/soc/amd/cezanne/fsp_m_params.c
@@ -36,6 +36,10 @@
 	return gfx_hda_dev->enabled;
 }
 
+__weak void mb_pre_fspm(void)
+{
+}
+
 static void fill_dxio_descriptors(FSP_M_CONFIG *mcfg,
 			const fsp_dxio_descriptor *descs, size_t num)
 {
@@ -171,4 +175,5 @@
 
 	fsp_fill_pcie_ddi_descriptors(mcfg);
 	fsp_assign_ioapic_upds(mcfg);
+	mb_pre_fspm();
 }