bnxt_en: Set async event bits when registering with the firmware.

Currently, the driver only sets bit 0 of the async_event_fwd fields.
To be compatible with the latest spec, we need to set the
appropriate event bits handled by the driver.  We should be handling
link change and PF driver unload events, so these 2 bits should be
set.

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