msm: sde: disable rotator bus scaling if not enabled

Allow bus scaling to be disabled if bus scaling table is
not defined in device tree or if bus scaling feature is
not enabled in device configuration.

CRs-Fixed: 2009714
Change-Id: I81d3c9d4874c43f67ade6773cd9f458f35010c5e
Signed-off-by: Alan Kwong <akwong@codeaurora.org>