tile: fix panic bug in napi support for tilegx network driver

The code used to call napi_disable() in an interrupt handler
(from smp_call_function), which in turn could call msleep().
Unfortunately you can't sleep in an interrupt context.

Luckily it turns out all the NAPI support functions are
just operating on data structures and not on any deeply
per-cpu data, so we can arrange to set up and tear down all
the NAPI state on the core driving the process, and just
do the IRQ enable/disable as a smp_call_function thing.

Signed-off-by: Chris Metcalf <cmetcalf@tilera.com>
Signed-off-by: David S. Miller <davem@davemloft.net>