nb/intel/broadwell/report_platform.c: Constify string array

Checkpatch suggests these changes when touching this code.

Change-Id: Ib85f4ca43b92a160519bd9e600054accaccc0e94
Signed-off-by: Angel Pons <th3fanbus@gmail.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/91623
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Matt DeVillier <matt.devillier@gmail.com>
Reviewed-by: Alicja Michalska <ahplka19@gmail.com>

src/northbridge/intel/broadwell/report_platform.c

@@ -74,7 +74,7 @@ static struct {
 
 static void report_cpu_info(void)
 {
-	const char *mode[] = {"NOT ", ""};
+	static const char *const mode[] = {"NOT ", ""};
 	const char *cpu_type = "Unknown";
 
 	char cpu_string[50];