drm: Add DRM_MODE_ROTATE_ and DRM_MODE_REFLECT_ to UAPI

Add DRM_MODE_ROTATE_ and DRM_MODE_REFLECT_ defines to the UAPI
as a convenience.

Ideally the DRM_ROTATE_ and DRM_REFLECT_ property ids are looked up
through the atomic API, but realizing that userspace is likely to take
shortcuts and assume that the enum values are what is sent over the
wire.

As a result these defines are provided purely as a convenience to
userspace applications.

Changes since v3:
 - Switched away from past tense in comments
 - Add define name change to previously mis-spelled DRM_REFLECT_X comment
 - Improved the comment for the DRM_MODE_REFLECT_<axis> comment

Changes since v2:
 - Changed define prefix from DRM_MODE_PROP_ to DRM_MODE_
 - Fix compilation errors
 - Changed comment formatting
 - Deduplicated comment lines
 - Clarified DRM_MODE_PROP_REFLECT_ comment

Changes since v1:
 - Moved defines from drm.h to drm_mode.h
 - Changed define prefix from DRM_ to DRM_MODE_PROP_
 - Updated uses of the defines to the new prefix
 - Removed include from drm_rect.c
 - Stopped using the BIT() macro

Signed-off-by: Robert Foss <robert.foss@collabora.com>
Reviewed-by: Emil Velikov <emil.velikov@collabora.com>
Reviewed-by: Sinclair Yeh <syeh@vmware.com>
Acked-by: Liviu Dudau <Liviu.Dudau@arm.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/20170519205017.23307-2-robert.foss@collabora.com