ice: add useful statistics

Display and count some useful hot-path statistics. The usefulness is as
follows:

- tx_restart: use to determine if the transmit ring size is too small or
  if the transmit interrupt rate is too low.
- rx_gro_dropped: use to count drops from GRO layer, which previously were
  completely uncounted when occurring.
- tx_busy: use to determine when the driver is miscounting number of
  descriptors needed for an skb.
- tx_timeout: as our other drivers, count the number of times we've reset
  due to timeout because the kernel only prints a warning once per netdev.

Several of these were already counted but not displayed.

Signed-off-by: Jesse Brandeburg <jesse.brandeburg@intel.com>
Tested-by: Andrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>