drm/i915: remove ICP_PP_CONTROL

This register was placed in the middle of the PP_STATUS definition
instead of together with the PP_CONTROL where it should. Since it's not
used and there are no current plans to use it, just remove the
definition.

v2: remove the define rather than moving it.

Signed-off-by: Lucas De Marchi <lucas.demarchi@intel.com>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190308232321.30168-1-lucas.demarchi@intel.com