fsck.cramfs: fix compiler warning

fsck.cramfs.c: In function ‘main’:
fsck.cramfs.c:676  warning: ‘length’ may be used uninitialized in this function

Signed-off-by: Karel Zak <kzak@redhat.com>

disk-utils/fsck.cramfs.c

@@ -673,7 +673,7 @@ int main(int argc, char **argv)
 {
 	int c;			/* for getopt */
 	int start = 0;
-	size_t length;
+	size_t length = 0;
 
 	page_size = getpagesize();