drm/i915: Delete duplicate #defines added for DCx

Delete the duplicate #defines introduced by:

	commit 6b457d31
	Author: A.Sunil Kamath <sunil.kamath@intel.com>
	Date:   Thu Apr 16 14:22:09 2015 +0530

		drm/i915/skl: Implement enable/disable for Display C5 state.

Signed-off-by: Chandra Konduru <chandra.konduru@intel.com>
Reviewed-by: Damien Lespiau <damien.lespiau@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>