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>

src/soc/amd/cezanne/fsp_m_params.c

@@ -36,6 +36,10 @@ static bool devtree_gfx_hda_dev_enabled(void)
 	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 @@ void platform_fsp_memory_init_params_cb(FSPM_UPD *mupd, uint32_t version)
 
 	fsp_fill_pcie_ddi_descriptors(mcfg);
 	fsp_assign_ioapic_upds(mcfg);
+	mb_pre_fspm();
 }

src/soc/amd/cezanne/include/soc/platform_descriptors.h

@@ -12,4 +12,6 @@ void mainboard_get_dxio_ddi_descriptors(
 		const fsp_dxio_descriptor **dxio_descs, size_t *dxio_num,
 		const fsp_ddi_descriptor **ddi_descs, size_t *ddi_num);
 
+void mb_pre_fspm(void);
+
 #endif /* AMD_PICASSO_PLATFORM_DESCRIPTORS_H */