security/intel/txt: use mca_get_bank_count()

Use the common mca_get_bank_count function instead of open-coding the
functionality to get the MCA bank number.

Change-Id: I28244c975ee34d36d0b44df092d4a62a01c3c79c
Signed-off-by: Felix Held <felix-coreboot@felixheld.de>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/56187
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Marshall Dawson <marshalldawson3rd@gmail.com>
diff --git a/src/security/intel/txt/common.c b/src/security/intel/txt/common.c
index 239e152..011e8cc 100644
--- a/src/security/intel/txt/common.c
+++ b/src/security/intel/txt/common.c
@@ -481,8 +481,7 @@
 		* Make sure there are no uncorrectable MCE errors.
 		* Intel 64 and IA-32 Architectures Software Developer Manuals Vol 2D
 		*/
-		msr = rdmsr(IA32_MCG_CAP);
-		size_t max_mc_msr = msr.lo & MCA_BANKS_MASK;
+		size_t max_mc_msr = mca_get_bank_count();
 		for (size_t i = 0; i < max_mc_msr; i++) {
 			msr = rdmsr(IA32_MC0_STATUS + 4 * i);
 			if (!(msr.hi & MCA_STATUS_HI_UC))