ice: update ICE_PHY_TYPE_HIGH_MAX_INDEX

ICE_PHY_TYPE_HIGH_MAX_INDEX should be the maximum index value and not the
length/number of ICE_PHY_TYPE_HIGH. This is not an issue because this
define is only used when calling ice_get_link_speed_based_on_phy_type(),
which will return ICE_AQ_LINK_SPEED_UNKNOWN for any invalid index. The
caller of ice_get_link_speed_based_on_phy_type(), ice_update_phy_type()
checks that the return value is a valid link speed before using it and
ICE_AQ_LINK_SPEED_UNKNOWN is not. However, update the define to reflect
the correct value.

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>