ext4: fix double locking in ext4_fc_commit_dentry_updates()

Fixed double locking of sbi->s_fc_lock in the above function
as reported by kernel-test-robot.

Signed-off-by: Harshad Shirwadkar <harshadshirwadkar@gmail.com>
Link: https://lore.kernel.org/r/20201023161339.1449437-1-harshadshirwadkar@gmail.com


Signed-off-by: Theodore Ts'o <tytso@mit.edu>