net: rps: fix uninitialized symbol warning

This patch fixes uninitialized symbol warning that
got introduced by the following commit
773fc8f6 ("net: rps: send out pending IPI's on CPU hotplug")

Signed-off-by: Ashwanth Goli <ashwanth@codeaurora.org>
Signed-off-by: David S. Miller <davem@davemloft.net>