msm: kgsl: Correctly derive RAM cycles from GBIF perf counters

GBIF has perf counters to count RAM cycles for each AXI channel
and access type separately unlike VBIF which has single perf
counter to count the total number of RAM cycles.

This change fixes the RAM cycles calculation from GBIF perf
counters by considering each channel READ/WRITE cycles.

Change-Id: I8307a92c1d936bb993aaef26b6b4ecd92537d16f
Signed-off-by: Deepak Kumar <dkumar@codeaurora.org>