drm/i915/kbl: Introduce Kabylake platform defition.

Kabylake is a Intel® Processor containing Intel® HD Graphics
following Skylake.

It is Gen9p5, so it inherits everything from Skylake.

Let's start by adding the platform separated from Skylake
but reusing most of all features, functions etc. Later we
rebase the PCI-ID patch without is_skylake=1
so we don't replace what original Author did there.

Few IS_SKYLAKEs if statements are not being covered by this patch
on purpose:
   - Workarounds: Kabylake is derivated from Skylake H0 so no
     		  W/As apply here.
   - GuC: A following patch removes Kabylake support with an
     	  explanation: No firmware available yet.
   - DMC/CSR: Done in a separated patch since we need to be carefull
     	      and load the version for revision 7 since
	      Kabylake is Skylake H0.

v2: relative cleaner commit message and added the missed
    IS_KABYLAKE to intel_i2c.c as pointed out by Jani.

Cc: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>