msm: kgsl: GPU soft reset

Soft reset GPU when GPU power rail is not turned off.
In hard reset we reload full microcode but in soft reset
since the memory powerrail is not turned off we only
load jump tables part of microcode, this reduces GPU
reset time from 10ms to 200us.

Change-Id: Ibbc36e97cc95425e13856fd5d847eed742743723
Signed-off-by: Tarun Karra <tkarra@codeaurora.org>