ice: refactor PHY type to ethtool link mode

Refactor ice_phy_type_to_ethtool to use phy_type_[low|high]_lkup table to
map PHY type to AQ link speed and ethtool link mode. This removes
complexity and simplifies future changes.

Signed-off-by: Paul Greenwalt <paul.greenwalt@intel.com>
Tested-by: Pucha Himasekhar Reddy <himasekharx.reddy.pucha@intel.com> (A Contingent worker at Intel)
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>