drm/i915: Fix PCH names for KBP and CNP.

No functional change.

KBP was based on SPT and spec wasn't clear about the full name.
There was the initial point of the "Point" confusion.

Later the split with Coffee Lake and Cannon Lake both using CNP
and also some uncertainty from the specs we had at that time
made us to propagated the mistake along.

So, let's fix this now and avoid propagating these wrong
"points".

Cc: Anusha Srivatsa <anusha.srivatsa@intel.com>
Cc: Paulo Zanoni <paulo.r.zanoni@intel.com>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Reviewed-by: Anusha Srivatsa <anusha.srivatsa@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20170731185220.758-1-rodrigo.vivi@intel.com