remove unlock_kernel() left accidentally

commit 337eb00a2c3a421999c39c94ce7e33545ee8baa7
Push BKL down into ->remount_fs()
and
commit 4aa98cf768b6f2ea4b204620d949a665959214f6
Push BKL down into do_remount_sb()

were uncorrectly merged.
The former removes one pair of lock/unlock_kernel(), but the latter adds
several unlock_kernel(). Finally a few unlock_kernel() calls left.

Signed-off-by: J. R. Okajima <hooanon05@yahoo.co.jp>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>