Fix uninitialized variable loop

The following command will usually just fail

 # /system/bin/mount -t proc proc /proc
 ioctl LOOP_SET_FD failed: Bad file number

The simple patch fixes the issue.

toolbox/mount.c

@@ -226,7 +226,7 @@ int mount_main(int argc, char *argv[])
 {
 	char *type = NULL;
 	int c;
-	int loop;
+	int loop = 0;
 
 	progname = argv[0];
 	rwflag = MS_VERBOSE;