disp: msm: sde: add dt property for QSEED scalar HW revision

QSEED scalar block HW revision is constant for a given MDSS revision.
Both SSPP and DS HW files invoke this API to read the revision register
at various points of time. Expose this revision information through
DT binding and maintain in the catalog to avoid repeated register
reads.

Change-Id: I95c0a5242cfda0aaa4ec5c2ff5c7cc0bed191b59
Signed-off-by: Jeykumar Sankaran <jsanka@codeaurora.org>