cifs: Fix SMB1 readv/writev callback in the same way as SMB2/3

Port a number of SMB2/3 async readv/writev fixes to the SMB1 transport:

    commit a88d6090
    cifs: Don't advance the I/O iterator before terminating subrequest

    commit ce5291e5
    cifs: Defer read completion

    commit 1da29f2c
    netfs, cifs: Fix handling of short DIO read

Fixes: 3ee1a1fc ("cifs: Cut over to using netfslib")
Signed-off-by: David Howells <dhowells@redhat.com>
Reported-by: Steve French <stfrench@microsoft.com>
Reviewed-by: Paulo Alcantara <pc@manguebit.com>
cc: Jeff Layton <jlayton@kernel.org>
cc: linux-cifs@vger.kernel.org
cc: netfs@lists.linux.dev
cc: linux-fsdevel@vger.kernel.org
Signed-off-by: Steve French <stfrench@microsoft.com>