jbd2: remove always true condition in __journal_try_to_free_buffer()

The check b_jlist == BJ_None in __journal_try_to_free_buffer() is
always true (__jbd2_journal_temp_unlink_buffer() also checks this in
an assertion) so just remove it.

Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>