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.
diff --git a/toolbox/mount.c b/toolbox/mount.c
index 395c943..472c952 100644
--- a/toolbox/mount.c
+++ b/toolbox/mount.c
@@ -226,7 +226,7 @@
 {
 	char *type = NULL;
 	int c;
-	int loop;
+	int loop = 0;
 
 	progname = argv[0];
 	rwflag = MS_VERBOSE;