drm/msm/shp: add shared plane support

Create a driver to create shared planes to SDE driver. In DRM lease
plane can't be passed from one master to another master seamlessly,
and plane resource will be wasted if one plane has finished its
lifecycle in one master and couldn't be used by another master
when they're both running.

A shared plane model is introduced by creating multiple virtual
planes from the physical plane. Only one virtual plane (including
the physical one) can be activated at a time. When handoff from one
master to another master is needed, the previous active plane will
be detached and the new plane will be activated in the same atomic
commit.

Change-Id: I26d2ab574783af8d4c0a751bfd82642be97280fc
Signed-off-by: Xiaowen Wu <wxiaowen@codeaurora.org>