drm: introduce share plane

drm: introduce share plane

The plane hardware is used when the display scanout run into plane active
scanout, that means we can reuse the plane hardware resources on plane
non-active scanout.

Because resource share, There are some limit on share plane: one group
of share planes need use same zpos, can't not overlap, etc.

We assume share plane is a universal plane with some limit flags.
people who use the share plane need know the limit, should call the ioctl
DRM_CLIENT_CAP_SHARE_PLANES, and judge the planes limit before use it.

Change-Id: Iecc3d8e7f1ce29d567cdbad689ba4dbad3d594e1
Signed-off-by: Mark Yao <mark.yao@rock-chips.com>