drm/i915/icl: Combine all port/combophy macros at one place

This patch combines CNL/ICL specific port/combophy macros together
at one location. This is prework for patches later in series where
new macros to find port/combophy register will be introduced.

v2: remove wrong empty line

Signed-off-by: Mahesh Kumar <mahesh1.kumar@intel.com>
Signed-off-by: Lucas De Marchi <lucas.demarchi@intel.com>
Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20181012234717.8284-1-lucas.demarchi@intel.com