bnxt_en: Do function reset on the 1st PF open only.

Calling the firmware to do function reset on the PF will kill all the VFs.
To prevent that, we call function reset on the 1st PF open before any VF
can be activated.  On subsequent PF opens (with possibly some active VFs),
a bit has been set and we'll skip the function reset.  VF driver will
always do function reset on every open.  If there is an AER event, we will
always do function reset.

Signed-off-by: Michael Chan <michael.chan@broadocm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>