bus/pci: resize interrupt event list only for MSIX

bus/pci: resize interrupt event list only for MSIX

Resizing event list only makes sense in MSIX case.

Besides, event list has always been RTE_MAX_RXTX_INTR_VEC_ID large.
Let's restore this assumption for code that might rely on this property
and only enlarge the event list when necessary.

Bugzilla ID: 843, 865
Fixes: 8cb5d08db940 ("interrupts: extend event list")
Signed-off-by: David Marchand <david.marchand@redhat.com>
Acked-by: Harman Kalra <hkalra@marvell.com>