[NET]: ethtool_perm_addr only has one implementation

All drivers implement ethtool get_perm_addr the same way -- by calling
the generic function.  So we can inline the generic function into the
caller and avoid going through the drivers.

Signed-off-by: Matthew Wilcox <matthew@wil.cx>
Signed-off-by: David S. Miller <davem@davemloft.net>