net: mvpp2: Fix affinity hint allocation

The mvpp2 driver has the curious behaviour of passing a stack variable
to irq_set_affinity_hint(), which results in the kernel exploding
the first time anyone accesses this information. News flash: userspace
does, and irqbalance will happily take the machine down. Great stuff.

An easy fix is to track the mask within the queue_vector structure,
and to make sure it has the same lifetime as the interrupt itself.

Fixes: e531f767 ("net: mvpp2: handle cases where more CPUs are available than s/w threads")
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>