cifs: remove useless DeleteMidQEntry()

DeleteMidQEntry() was just a proxy for cifs_mid_q_entry_release().

- remove DeleteMidQEntry()
- rename cifs_mid_q_entry_release() to release_mid()
- rename kref_put() callback _cifs_mid_q_entry_release to __release_mid
- rename AllocMidQEntry() to alloc_mid()
- rename cifs_delete_mid() to delete_mid()

Update callers to use new names.

Signed-off-by: Enzo Matsumiya <ematsumiya@suse.de>
Signed-off-by: Steve French <stfrench@microsoft.com>