net/qede: skip slow path polling for 100G VF device

There is no need to poll for slowpath events for VF
device since the ramrod responses are received over
PF-VF backchannel synchronously. So the fix is to
restrict the slowpath polling for PF device only.

Fixes: 2af14ca79c0a ("net/qede: support 100G")
Signed-off-by: Harish Patil <harish.patil@qlogic.com>