f2fs: remove pointless bit testing in f2fs_delete_entry()

There's no point in using test_and_clear_bit_le() when we don't use the
return value of the function. Just use clear_bit_le() instead.

Coverity-id: 1016434
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>