[NETPOLL]: Remove CONFIG_NETPOLL_RX

Get rid of the CONFIG_NETPOLL_RX option completely since all the
dependencies have been removed long ago...

Signed-off-by: Sergei Shtylyov <sshtylyov@ru.mvista.com>
Acked-by: Jeff Garzik <jgarzik@pobox.com>
Acked-by: Matt Mackall <mpm@selenic.com>
Signed-off-by: David S. Miller <davem@davemloft.net>