ice: ignore dropped packets during init

If the hardware is constantly receiving unicast or broadcast packets
during driver load, the device previously counted many GLV_RDPC (VSI
dropped packets) events during init. This causes confusing dropped
packet statistics during driver load. The dropped packets counter
incrementing does stop once the driver finishes loading.

Avoid this problem by baselining our statistics at the end of driver
open instead of the end of probe.

Fixes: cdedef59 ("ice: Configure VSIs for Tx/Rx")
Signed-off-by: Jesse Brandeburg <jesse.brandeburg@intel.com>
Tested-by: Gurucharan G <gurucharanx.g@intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>