msm: kgsl: Add missing check for snapshot IB dump

During ringbuffer parsing, same IB can exist multiple times
but size validation happens only for the first time.
This leads to out of bound access if the subsequent sizes are
greater than the allocated size.

Add a check to make sure that requested size is within the
allocated range.

Change-Id: Ie5d3c02c1669de2e6188821399e985f0991aa57c
Signed-off-by: Rajesh Kemisetti <rajeshk@codeaurora.org>