drm/i915/icp: add ICP gmbus and gpio support

drm/i915/icp: add ICP gmbus and gpio support

In ICP, there are three TC ports and 3 DDI ports.

v2:
 - Correct Pin mapping.
v3:
 - Update pin mapping into per platform implementation
   rather than previous approach of port wise mapping.
v4:
 - Update GMBUS_NUM_PINS (Paulo)
v5:
 - rebase.
v6:
 - Update function name, GMBUS_PIN_NUM (Paulo)
v7 (from Paulo):
 - Make it apply.
v8 (from Paulo):
 - Maintain consistent if ladder ordering.

Suggested by: Ville Syrjala <ville.syrjala@linux.intel.com>
Cc: Jani Nikula <jani.nikula@intel.com>
Reviewed-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
Signed-off-by: Anusha Srivatsa <anusha.srivatsa@intel.com>
Signed-off-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180111180010.24357-8-paulo.r.zanoni@intel.com