jffs2: remove from wait queue after schedule()

commit 3ead9578443b66ddb3d50ed4f53af8a0c0298ec5 upstream.

@wait is a local variable, so if we don't remove it from the wait queue
list, later wake_up() may end up accessing invalid memory.

This was spotted by eyes.

Change-Id: I1f97a1eaa19eb88ec4156ffba4cdfe477dad117d
Signed-off-by: Li Zefan <lizefan@huawei.com>
Cc: David Woodhouse <dwmw2@infradead.org>
Cc: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Brian Norris <computersforpeace@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>