msm: kgsl: Omit referencing pointers in traces

Trace points should not store pointers in the trace data because
they could be dereferenced much later after the original memory
has disappeared.

Change-Id: I9f134bcdaa39c437394c3552aaacd8a360924200
Signed-off-by: Harshdeep Dhatt <hdhatt@codeaurora.org>