soc/intel/skylake: Hook up IGD config to option API

Hook up the IGD config options IgdDvmt50PreAlloc and ApertureSize to the
option API, so they can be configured at runtime without recompilation.

The Aperture size falls back to the FSP default value, so no change if
unconfigured.

Change-Id: Ic900cb7bdc6dc532aef0c0b51b32bf8308a8ae36
Signed-off-by: Matt DeVillier <matt.devillier@gmail.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/87392
Reviewed-by: Jérémy Compostella <jeremy.compostella@intel.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

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

@@ -116,7 +116,8 @@ static void soc_primary_gfx_config_params(FSP_M_CONFIG *m_cfg,
 	 *
 	 * If disabled, don't reserve memory for it.
 	 */
-	m_cfg->IgdDvmt50PreAlloc = m_cfg->InternalGfx ? 2 : 0;
+	m_cfg->IgdDvmt50PreAlloc = m_cfg->InternalGfx ? get_uint_option("igd_dvmt_prealloc", 2) : 0;
+	m_cfg->ApertureSize = get_uint_option("igd_aperture_size", 1);
 
 	m_cfg->PrimaryDisplay = config->PrimaryDisplay;
 }