jbd2: Drop jbd2_space_needed()

The function is now just a trivial wrapper returning
journal->j_max_transaction_buffers. Drop it.

Reviewed-by: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Jan Kara <jack@suse.cz>
Link: https://lore.kernel.org/r/20191105164437.32602-19-jack@suse.cz


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