jbd2: remove journal_t argument from jbd2_superblock_csum()

Since jbd2_superblock_csum() no longer uses its journal_t argument,
remove it.

Signed-off-by: Eric Biggers <ebiggers@google.com>
Reviewed-by: Baokun Li <libaokun1@huawei.com>
Link: https://patch.msgid.link/20250513053809.699974-5-ebiggers@kernel.org


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