msm: kgsl: use the same logic in adreno_idle and adreno_isidle

These two functions need to agree on the meaning of "idle",
so that calling adreno_isidle() right after an adreno_idle()
will always return true.

Also, use msecs_to_jiffies for ADRENO_IDLE_TIMEOUT

Signed-off-by: Jeremy Gebben <jgebben@codeaurora.org>
(cherry picked from commit 5365240)
Signed-off-by: Harsh Vardhan Dwivedi <hdwivedi@codeaurora.org>
Signed-off-by: Sridhar Gujje <sgujje@codeaurora.org>
Signed-off-by: Hareesh Gundu <hareeshg@codeaurora.org>