drm/i915/crc: move pipe_crc from drm_i915_private to intel_crtc

Having an array pipe_crc[I915_MAX_PIPES] in struct drm_i915_private
should be an obvious clue this should be located in struct intel_crtc
instead. Make it so.

As a side-effect, fix some errors in indexing pipe_crc with both pipe
and crtc index. And, of course, reduce the size of i915_drv.h.

Cc: Anshuman Gupta <anshuman.gupta@intel.com>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200227161253.15741-1-jani.nikula@intel.com