bnxt_en: Add PHY retry logic.

During hotplug, the driver's open function can be called almost
immediately after power on reset.  The PHY may not be ready and the
firmware may return failure when the driver tries to update PHY
settings.  Add retry logic fired from the driver's timer to retry
the operation for 5 seconds.

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