msm: kgsl: Enable dynamic bus scaling for the GPU

With the addition of GMU it is no longer known by KGSL
if the bus is on or off.  Do not allow the on/off bus
flag to affect decisions on GMU targets.

CRs-Fixed: 2062271
Change-Id: I1fccdeee5fa94ac9dea8ae1c424d97650a5b3756
Signed-off-by: Lucille Sylvester <lsylvest@codeaurora.org>
Signed-off-by: Oleg Perelet <operelet@codeaurora.org>
Signed-off-by: George Shen <sqiao@codeaurora.org>