x86/acpi: Add BERT to the revision table

Add the proper table revision level for the Boot Error Record Table.

BUG=b:65446699
TEST=inspect BERT region, and dmesg, on full patch stack.  Use test
    data plus a failing Grunt system.

Change-Id: Ib4596fe8c0dd2a4e2e98df3a1bb60803c48d0256
Signed-off-by: Marshall Dawson <marshalldawson3rd@gmail.com>
Reviewed-on: https://review.coreboot.org/28471
Reviewed-by: Martin Roth <martinroth@google.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

src/arch/x86/acpi.c

@@ -1296,6 +1296,8 @@ int get_acpi_table_revision(enum acpi_tables table)
 		return 1;
 	case NHLT:
 		return 5;
+	case BERT:
+		return 1;
 	default:
 		return -1;
 	}