SUNPRC: remove marking service temporary sockets with XPT_CHNGBUF

This is a cleanup patch.
Service temporary sockets can be TCP or RDMA only. But XPT_CHNGBUF service
socket flag is checked only for UDP sockets on receive.
Thus (if I don't miss something non-obvious) this bit raising for temporary
sockets can be removed.

Signed-off-by: Stanislav Kinsbursky <skinsbursky@parallels.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>