Fix gcc7 complaining about memset()

firmware.c: In function 'firmware_dump':
firmware.c:112:3: error: 'memset' used with length equal to number of
                  elements without multiplication by element size
                  [-Werror=memset-elt-size]
   memset(all_ff, 255, 256);
   ^~~~~~

Change-Id: I10da0fed537125d10ac81484e26701a5f163bfe9
Signed-off-by: Stefan Reinauer <stefan.reinauer@coreboot.org>
Reviewed-on: https://review.coreboot.org/22544
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Martin Roth <martinroth@google.com>
diff --git a/firmware.c b/firmware.c
index 775029d..5f66c65 100644
--- a/firmware.c
+++ b/firmware.c
@@ -104,12 +104,12 @@
 
 	if (firmware_is_dpfw) {
 		int fpga_size = 0, mcu_size = 0;
-		char *all_ff[256];
+		char all_ff[256];
 		char mcu_version[8];
 		char fpga_version[8];
 		unsigned char header[0x100];
 
-		memset(all_ff, 255, 256);
+		memset(all_ff, 255, 256 * sizeof(char));
 		for (i = 0; i < 0x100000; i+=0x100) {
 			if (memcmp(data+i, all_ff, 256) == 0)
 				break;