{cpu/x86, drivers/amd}: Use `get_var_mtrr_count()` to get MTRR count

This patch replaces the implementation that is used to get the number of
variable MTRRs with `get_var_mtrr_count()` function.

BUG=b:225766934
TEST=Able to build and boot google/redrix board to ChromeOS.

Signed-off-by: Subrata Banik <subratabanik@google.com>
Change-Id: I4751add9c45374e60b7a425df87d06f52e6fcb8c
Reviewed-on: https://review.coreboot.org/c/coreboot/+/63219
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Felix Held <felix-coreboot@felixheld.de>
Reviewed-by: Arthur Heymans <arthur@aheymans.xyz>
Reviewed-by: Eric Lai <eric_lai@quanta.corp-partner.google.com>
Reviewed-by: Tim Wawrzynczak <twawrzynczak@chromium.org>

src/cpu/x86/mp_init.c

@@ -247,11 +247,9 @@ static int save_bsp_msrs(char *start, int size)
 	int num_var_mtrrs;
 	struct saved_msr *msr_entry;
 	int i;
-	msr_t msr;
 
 	/* Determine number of MTRRs need to be saved. */
-	msr = rdmsr(MTRR_CAP_MSR);
-	num_var_mtrrs = msr.lo & 0xff;
+	num_var_mtrrs = get_var_mtrr_count();
 
 	/* 2 * num_var_mtrrs for base and mask. +1 for IA32_MTRR_DEF_TYPE. */
 	msr_count = 2 * num_var_mtrrs + NUM_FIXED_MTRRS + 1;

src/cpu/x86/mtrr/mtrr.c

@@ -41,11 +41,7 @@ static int total_mtrrs;
 
 static void detect_var_mtrrs(void)
 {
-	msr_t msr;
-
-	msr = rdmsr(MTRR_CAP_MSR);
-
-	total_mtrrs = msr.lo & 0xff;
+	total_mtrrs = get_var_mtrr_count();
 
 	if (total_mtrrs > NUM_MTRR_STATIC_STORAGE) {
 		printk(BIOS_WARNING,

src/cpu/x86/mtrr/xip_cache.c

@@ -14,8 +14,7 @@
    the MTRR, no matter the caching type, are filled and not overlapping. */
 static uint32_t max_cache_used(void)
 {
-	msr_t msr = rdmsr(MTRR_CAP_MSR);
-	int i, total_mtrrs = msr.lo & MTRR_CAP_VCNT;
+	int i, total_mtrrs = get_var_mtrr_count();
 	uint32_t total_cache = 0;
 
 	for (i = 0; i < total_mtrrs; i++) {

src/drivers/amd/agesa/mtrr_fixme.c

@@ -14,8 +14,7 @@ static void set_range_uc(u32 base, u32 size)
 {
 	int i, max_var_mtrrs;
 	msr_t msr;
-	msr = rdmsr(MTRR_CAP_MSR);
-	max_var_mtrrs = msr.lo & MTRR_CAP_VCNT;
+	max_var_mtrrs = get_var_mtrr_count();
 
 	for (i = 0; i < max_var_mtrrs; i++) {
 		msr = rdmsr(MTRR_PHYS_MASK(i));