drm/msm/sde: add support for Smart DMA v2.5

This patch exposes Smart DMA version 2.5 to user-space clients for
targets which support this version based on the value read from the
device tree node.

Change-Id: I08caaf2433f978d89b71654aeef66c70fbe2cd95
Signed-off-by: Steve Cohen <cohens@codeaurora.org>