soc/intel/alderlake: Implement PMC soft strap interface lock

This patch performs locking of the PMC soft strap message interface.

BUG=b:211954778
TEST=Able to build and boot google/redrix to OS. Verified Bit 0 of PMC
MMIO register 0x104c is set as below.

> localhost ~ # iotools mmio_read32 0xfe00104c
0x00000001

Signed-off-by: Subrata Banik <subratabanik@google.com>
Change-Id: I1ae972a203affa54c03de71f0f702356334cbf7d
Reviewed-on: https://review.coreboot.org/c/coreboot/+/63690
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Lean Sheng Tan <sheng.tan@9elements.com>
Reviewed-by: Eric Lai <eric_lai@quanta.corp-partner.google.com>
Reviewed-by: Angel Pons <th3fanbus@gmail.com>
diff --git a/src/soc/intel/alderlake/lockdown.c b/src/soc/intel/alderlake/lockdown.c
index 5d012d8..f018dbd 100644
--- a/src/soc/intel/alderlake/lockdown.c
+++ b/src/soc/intel/alderlake/lockdown.c
@@ -24,8 +24,10 @@
 	if (chipset_lockdown == CHIPSET_LOCKDOWN_COREBOOT)
 		setbits32(pmcbase + GEN_PMCON_B, SMI_LOCK);
 
-	if (!CONFIG(USE_FSP_NOTIFY_PHASE_POST_PCI_ENUM))
+	if (!CONFIG(USE_FSP_NOTIFY_PHASE_POST_PCI_ENUM)) {
 		setbits32(pmcbase + ST_PG_FDIS1, ST_FDIS_LOCK);
+		setbits32(pmcbase + SSML, SSML_SSL_EN);
+	}
 }
 
 void soc_lockdown_config(int chipset_lockdown)