drm/msm: return correct error for rsc state switching

The switch to clk and vid states for rsc should return an
integer type and not a boolean to allow the internal
caller to differentiate between "update not allowed" and
real underlying errors.

CRs-Fixed: 2048128
Change-Id: I16cf17e74556659b9c6946304730ef2f74370529
Signed-off-by: Clarence Ip <cip@codeaurora.org>