cifs: smbd: Check for iov length on sending the last iov

cifs: smbd: Check for iov length on sending the last iov

commit ab60ee7bf9a84954f50a66a3d835860e80f99b7f upstream.

When sending the last iov that breaks into smaller buffers to fit the
transfer size, it's necessary to check if this is the last iov.

If this is the latest iov, stop and proceed to send pages.

Signed-off-by: Long Li <longli@microsoft.com>
Cc: stable@vger.kernel.org
Signed-off-by: Steve French <stfrench@microsoft.com>
Reviewed-by: Ronnie Sahlberg <lsahlber@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>