ext4: factor out a helper to check the cluster allocation state

Factor out a common helper ext4_clu_alloc_state(), check whether the
cluster containing a delalloc block to be added has been allocated or
has delalloc reservation, no logic changes.

Signed-off-by: Zhang Yi <yi.zhang@huawei.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Link: https://patch.msgid.link/20240517124005.347221-9-yi.zhang@huaweicloud.com


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