soc/skl: Update SkipExtGfxScan in UPD from devtree

The SkipExtGfxScan option is defined in the device tree, but doesn`t
update the value in the UPD. It uses the default value - 0. This
means that the FSP will scan all external graphics devices, in spite
of the configuration in devicetree.cb for a specific board.

Patch updates SkipExtGfxScan options in UPD from devicetree.cb.
This change affects all boards with skl/kbl processor.

Change-Id: Ie88a41bdf31f7c3e88df6c70c82a1cbf866372c4
Signed-off-by: Maxim Polyakov <max.senia.poliak@gmail.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/32170
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Nico Huber <nico.h@gmx.de>

src/soc/intel/skylake/romstage/romstage_fsp20.c

@@ -354,6 +354,7 @@ void platform_fsp_memory_init_params_cb(FSPM_UPD *mupd, uint32_t version)
 
 	/* Set primary graphic device */
 	soc_primary_gfx_config_params(m_cfg, config);
+	m_t_cfg->SkipExtGfxScan = config->SkipExtGfxScan;
 
 	mainboard_memory_init_params(mupd);
 }