haswell: Clear correct number of MCA banks

The configure_mca() function was hard coding the number of
banks the cpu supported. Query this dynamically so that it
no longer clears only 7 banks.

Change-Id: I33fce8fadc0facd1016b3295faaf3ae90e490a71
Signed-off-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-on: http://review.coreboot.org/2745
Tested-by: build bot (Jenkins)
Reviewed-by: Ronald G. Minnich <rminnich@gmail.com>
diff --git a/src/cpu/intel/haswell/haswell_init.c b/src/cpu/intel/haswell/haswell_init.c
index 762b7e8..45c1a25 100644
--- a/src/cpu/intel/haswell/haswell_init.c
+++ b/src/cpu/intel/haswell/haswell_init.c
@@ -424,11 +424,17 @@
 static void configure_mca(void)
 {
 	msr_t msr;
+	const unsigned int mcg_cap_msr = 0x179;
 	int i;
+	int num_banks;
 
+	msr = rdmsr(mcg_cap_msr);
+	num_banks = msr.lo & 0xff;
 	msr.lo = msr.hi = 0;
-	/* This should only be done on a cold boot */
-	for (i = 0; i < 7; i++)
+	/* TODO(adurbin): This should only be done on a cold boot. Also, some
+	 * of these banks are core vs package scope. For now every CPU clears
+	 * every bank. */
+	for (i = 0; i < num_banks; i++)
 		wrmsr(IA32_MC0_STATUS + (i * 4), msr);
 }