cifs: remove struct smb2_oplock_break_rsp

The two structures smb2_oplock_breaq_req/rsp are now basically identical.
Replace this with a single definition of a smb2_oplock_break structure.

Signed-off-by: Ronnie Sahlberg <lsahlber@redhat.com>
Signed-off-by: Steve French <stfrench@microsoft.com>