soc/intel/cmn/pch/lockdown: Guard gpmr_lockdown_cfg

Guard gpmr_lockdown_cfg with SOC_INTEL_COMMON_BLOCK_GPMR
so it doesn't run on platforms that don't select this.

Signed-off-by: Sean Rhodes <sean@starlabs.systems>
Change-Id: Iab5bbd399c3a654dcb95eaa8fce683a50c7322f2
Reviewed-on: https://review.coreboot.org/c/coreboot/+/65227
Reviewed-by: Angel Pons <th3fanbus@gmail.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Lean Sheng Tan <sheng.tan@9elements.com>

src/soc/intel/common/pch/lockdown/lockdown.c

@@ -29,6 +29,9 @@ int get_lockdown_config(void)
 
 static void gpmr_lockdown_cfg(void)
 {
+	if (!CONFIG(SOC_INTEL_COMMON_BLOCK_GPMR))
+		return;
+
 	/*
 	 * GCS reg
 	 *