igc: Fix overwrites when dumping registers

This patch fixes some register overwriting when dumping registers via
ethtool.

We have a total of 16 RAL registers, starting at offset 139. So RAH
offset should be 139 + 16 = 155, not 145. As result some RAL registers
are overwritten. Likewise, RAH registers are also overwritten by TDBAL,
TDBAH, TDLEN, and TDH registers.

To fix this bug while preserving the ABI, this patch re-writes RAL and
RAH registers at the end of 'regs_buff' and bumps regs->version. It also
removes some pointless comments in the middle of igc_set_regs().

Signed-off-by: Andre Guedes <andre.guedes@intel.com>
Tested-by: Aaron Brown <aaron.f.brown@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>