soc/intel/alderlake: Disable L1 substates for PCIe compliance test mode

Disable L1 substates for PCIe compliance test mode in order to get
continuous clock output.

BUG=b:235863379
TEST=Boot in compliance mode, check FSP settings

Signed-off-by: Bora Guvendik <bora.guvendik@intel.corp-partner.google.com>
Change-Id: I2a3b313425e00fe11f616d964f825baaef463c71
Reviewed-on: https://review.coreboot.org/c/coreboot/+/70165
Reviewed-by: Jérémy Compostella <jeremy.compostella@intel.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Nick Vaccaro <nvaccaro@google.com>
diff --git a/src/soc/intel/alderlake/fsp_params.c b/src/soc/intel/alderlake/fsp_params.c
index 853b2f2..224cf8a 100644
--- a/src/soc/intel/alderlake/fsp_params.c
+++ b/src/soc/intel/alderlake/fsp_params.c
@@ -471,7 +471,9 @@
  */
 static int get_l1_substate_control(enum L1_substates_control ctl)
 {
-	if ((ctl > L1_SS_L1_2) || (ctl == L1_SS_FSP_DEFAULT))
+	if (CONFIG(SOC_INTEL_COMPLIANCE_TEST_MODE))
+		ctl = L1_SS_DISABLED;
+	else if ((ctl > L1_SS_L1_2) || (ctl == L1_SS_FSP_DEFAULT))
 		ctl = L1_SS_L1_2;
 	return ctl - 1;
 }