Changes:
- Fix: In ethtool.8, remove superfluous and incorrect \c.
- Fix: fix uninitialized return value
- Fix: fix RING_VF assignment
- Fix: remove unused global variable
- Fix: several fixes in do_gregs()
- Fix: correctly free hkey when get_stringset() fails
- Fix: remove unreachable code
- Fix: fix stack clash in do_get_phy_tunable and do_set_phy_tunable
- Feature: Add register dump support for MICROCHIP LAN78xx