xps: Add CONFIG_XPS

This patch adds XPS_CONFIG option to enable and disable XPS.  This is
done in the same manner as RPS_CONFIG.  This is also fixes build
failure in XPS code when SMP is not enabled.

Signed-off-by: Tom Herbert <therbert@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --cc include/linux/netdevice.h
Simple merge

diff --cc net/Kconfig
Simple merge

diff --cc net/core/dev.c
Simple merge

diff --cc net/core/net-sysfs.c
Simple merge

diff --cc net/core/net-sysfs.h
Simple merge