jbd2: remove unused parameter in jbd2_journal_try_to_free_buffers()

Parameter gfp_mask in jbd2_journal_try_to_free_buffers() is no longer
used after commit <536fc240> ("jbd2: clean up
jbd2_journal_try_to_free_buffers()"), so just remove it.

Signed-off-by: zhangyi (F) <yi.zhang@huawei.com>
Link: https://lore.kernel.org/r/20200620025427.1756360-6-yi.zhang@huawei.com


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