x86/mce, acpi/apei: Only disable banks listed in HEST if mce is configured

Randconfig testing found this build error:

 >> hest.c(.init.text+0x6004): undefined reference to 'mce_disable_bank'

Fix by wrapping body of hest_parse_cmc() inside #ifdef
CONFIG_X86_MCE

Reported-by: "Wu, Fengguang" <fengguang.wu@intel.com>
Signed-off-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>
Acked-by: Borislav Petkov <bp@alien8.de>
Link: http://lkml.kernel.org/r/0129220@agluck-desk.sc.intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

drivers/acpi/apei/hest.c

@@ -128,6 +128,7 @@ EXPORT_SYMBOL_GPL(apei_hest_parse);
  */
 static int __init hest_parse_cmc(struct acpi_hest_header *hest_hdr, void *data)
 {
+#ifdef CONFIG_X86_MCE
 	int i;
 	struct acpi_hest_ia_corrected *cmc;
 	struct acpi_hest_ia_error_bank *mc_bank;
@@ -152,7 +153,7 @@ static int __init hest_parse_cmc(struct acpi_hest_header *hest_hdr, void *data)
 	mc_bank = (struct acpi_hest_ia_error_bank *)(cmc + 1);
 	for (i = 0; i < cmc->num_hardware_banks; i++, mc_bank++)
 		mce_disable_bank(mc_bank->bank_number);
-
+#endif
 	return 1;
 }