net/avp: handle interrupt migration

net/avp: handle interrupt migration

This commit introduces changes required to support VM live-migration.  This
is done by registering and responding to interrupts coming from the host to
signal that the memory is about to be made invalid and replaced with a new
memory zone on the destination compute node.

Enabling and disabling of the interrupts are maintained outside of the
start/stop functions because they must be enabled for the lifetime of the
device.  This is so that host interrupts are serviced and acked even in
cases where the app may have stopped the device.

Signed-off-by: Allain Legacy <allain.legacy@windriver.com>
Signed-off-by: Matt Peters <matt.peters@windriver.com>
Acked-by: Vincent Jardin <vincent.jardin@6wind.com>