drm/i915: Make MG PHY macros semantically consistent

Organize MG PHY macro definitions semantically based on dword, lane and
port (in this order).

Cc: Clint Taylor <clinton.a.taylor@intel.com>
Cc: Imre Deak <imre.deak@intel.com>
Cc: Jani Nikula <jani.nikula@linux.intel.com>
Signed-off-by: Aditya Swarup <aditya.swarup@intel.com>
Reviewed-by: Manasi navare <manasi.d.navare@intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190128220012.13122-3-aditya.swarup@intel.com