arch/frv/kernel/setup.c: use strncmp() instead of memcmp()

'cmdline' is a NUL terminated string, when its length < 4, memcmp()
will cause memory access out of boundary.

So use strncmp() instead of memcmp().
Signed-off-by: Chen Gang <gang.chen@asianux.com>
Cc: David Howells <dhowells@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

arch/frv/kernel/setup.c

@@ -735,7 +735,7 @@ static void __init parse_cmdline_early(char *cmdline)
 		/* "mem=XXX[kKmM]" sets SDRAM size to <mem>, overriding the value we worked
 		 * out from the SDRAM controller mask register
 		 */
-		if (!memcmp(cmdline, "mem=", 4)) {
+		if (!strncmp(cmdline, "mem=", 4)) {
 			unsigned long long mem_size;
 
 			mem_size = memparse(cmdline + 4, &cmdline);