ibmvnic: Only do H_EOI for mobility events

When enabling the sub-CRQ IRQ a previous update sent a H_EOI prior
to the enablement to clear any pending interrupts that may be present
across a partition migration. This fixed a firmware bug where a
migration could erroneously indicate that a H_EOI was pending.

The H_EOI should only be sent when enabling during a mobility
event though. Doing so at other time could wrong and can produce
extra driver output when IRQs are enabled when doing TX completion.

Signed-off-by: Nathan Fontenot <nfont@linux.vnet.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>