sunrcp: make function _svc_create_xprt static

The function _svc_create_xprt is local to the source and
does not need to be in global scope, so make it static.

Cleans up sparse warning:
symbol '_svc_create_xprt' was not declared. Should it be static?

Signed-off-by: Colin Ian King <colin.king@canonical.com>
Reviewed-by: Jeff Layton <jlayton@poochiereds.net>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>