ext4: convert EXT4_FLAGS_* defines to enum

Do away with the defines and use an enum as it's cleaner.

Signed-off-by: Baokun Li <libaokun1@huawei.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Reviewed-by: Zhang Yi <yi.zhang@huawei.com>
Link: https://patch.msgid.link/20250122114130.229709-2-libaokun@huaweicloud.com


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