drm/msm/sde: add support for smart DMA 2.0

SmartDMA allows fetching multiple surfaces in a single source pipe.
SmartDMA version 2.0 can fetch up to 2 surfaces in a single pipe for
2 destination rectangles. This change adds support for this feature
in SDE DRM. Each destination rectangle path of a smartDMA pipe is
enumerated as a separate DRM plane with necessary property to
indicate the pair. Clients need to identify the pair and program the
source surfaces as per the HW limitations of the version supported.
SmartDMA will be enabled only on requesting SDE customization by
kernel-clients.

Change-Id: Ic0a0496cb785d6212e375cc7e0fc55407f7d8a0b
Signed-off-by: Jeykumar Sankaran <jsanka@codeaurora.org>