libdrm: Add rotation property fields

From drm_crtc.h, for use with the plane "rotation" property

NOTE: These are legacy definitions for old code, similar
DRM_MODE_* mask values are defined in the upstream code.

Change-Id: I9240dede6a53817e6d8cedb31f6877312078b5ab
Signed-off-by: Sean Paul <seanpaul@chromium.org>
[jstultz: Added note about legacy definitions ]
Signed-off-by: John Stultz <john.stultz@linaro.org>