msm: kgsl: Snapshot the correct amount of CP ROQ data

Read the CP ROQ size from a register (rather than hard coding for
each A6XX target) and then snapshot the correct amount.

Change-Id: I9d127813d8e92e9321e85bd28cb8cd83ac14d3ab
Signed-off-by: Carter Cooper <ccooper@codeaurora.org>