jbd2: add prefix 'jbd2' for 'shrink_type'

As 'shrink_type' is exported. The module prefix 'jbd2' is added to
distinguish from memory reclamation.

Signed-off-by: Ye Bin <yebin10@huawei.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Reviewed-by: Zhang Yi <yi.zhang@huawei.com>
Link: https://lore.kernel.org/r/20240407065355.1528580-3-yebin10@huawei.com
Signed-off-by: Theodore Ts'o <tytso@mit.edu>