jffs2: fix spelling mistake "neccecary"->"necessary"

There is a spelling mistake in comment. Fix it.
Signed-off-by: Yu Zhe <yuzhe@nfschina.com>
Signed-off-by: Richard Weinberger <richard@nod.at>

fs/jffs2/fs.c

@@ -403,7 +403,7 @@ int jffs2_do_remount_fs(struct super_block *sb, struct fs_context *fc)
 	/* We stop if it was running, then restart if it needs to.
 	   This also catches the case where it was stopped and this
 	   is just a remount to restart it.
-	   Flush the writebuffer, if neccecary, else we loose it */
+	   Flush the writebuffer, if necessary, else we loose it */
 	if (!sb_rdonly(sb)) {
 		jffs2_stop_garbage_collect_thread(c);
 		mutex_lock(&c->alloc_sem);