bnxt_en: Exclude rx_drop_pkts hw counter from the stack's rx_dropped counter.

This hardware counter is misleading as it counts dropped packets that
don't match the hardware filters for unicast/broadcast/multicast.  We
will still report this counter in ethtool -S for diagnostics purposes.

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