soc/intel/common/mp_init: Fix USE_INTEL_FSP_MP_INIT use-case

Commit 829e8e65b9 ("soc/intel: Use common codeflow for MP init")
brokes `USE_INTEL_FSP_MP_INIT' by making `init_cpus' function
static. This function needs to be accessible from
src/drivers/intel/fsp2_0/fsp_mpinit.c.

TEST=Verified on Meteor Lake rex board

Change-Id: Idb8cdfef7b4279da2c7dff344c95fe446a605934
Signed-off-by: Jeremy Compostella <jeremy.compostella@intel.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/80575
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Subrata Banik <subratabanik@google.com>

src/soc/intel/common/block/cpu/mp_init.c

@@ -147,7 +147,7 @@ void get_microcode_info(const void **microcode, int *parallel)
  * creation of the new node will be skipped. This node will have the APIC ID defined
  * in devicetree.
  */
-static void init_cpus(void)
+void init_cpus(void)
 {
 	struct device *dev = dev_find_path(NULL, DEVICE_PATH_CPU_CLUSTER);
 	assert(dev != NULL);

src/soc/intel/common/block/include/intelblocks/mp_init.h

@@ -23,6 +23,16 @@ int get_cpu_count(void);
  */
 void get_microcode_info(const void **microcode, int *parallel);
 
+/*
+ * Perform BSP and AP initialization
+ * This function can be called in below cases
+ * 1. During coreboot is doing MP initialization as part of BS_DEV_INIT_CHIPS (exclude
+ * this call if user has selected USE_INTEL_FSP_MP_INIT)
+ * 2. coreboot would like to take APs control back after FSP-S has done with MP
+ * initialization based on user select USE_INTEL_FSP_MP_INIT
+ */
+void init_cpus(void);
+
 /*
  * This function will perform any recommended CPU (BSP and AP) initialization
  * after coreboot has done the multiprocessor initialization (before FSP-S)