UPSTREAM: fs: provide locked helper variant of close_fd_get_file()

[ Upstream commit 53dec2ea ]

Assumes current->files->file_lock is already held on invocation. Helps
the caller check the file before removing the fd, if it needs to.

Change-Id: Idd87700a119403ce3867aa52294a14213b505faa
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
(cherry picked from commit d2136fc1)
Bug: 268174392
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>