msm: kgsl: Enable ISDB mode

Allow the user to set ISDB mode to disable various timers and allow
shader debugging.

"echo 1 > /sys/kernel/debug/kgsl/kgsl-3d0/isdb"

Change-Id: Ic0dedbadea3475ed1b0122d06f62db6f09cc34a3
Signed-off-by: Jordan Crouse <jcrouse@codeaurora.org>
Signed-off-by: Lokesh Batra <lbatra@codeaurora.org>
Signed-off-by: Tarun Karra <tkarra@codeaurora.org>