msm: kgsl: Run the idle timer while the GPU is not power collapsed

If the GPU is not in its lowest permitted power collapse state,
make sure there is a timer running to get the GPU to that state.

Change-Id: If57aaaf02087036bc4e24725c0cd3de5bc1f1034
Signed-off-by: Lucille Sylvester <lsylvest@codeaurora.org>