msm: kgsl: rework ib checking

Separate ib parse checking from cffdump as it is useful
in other situations. This is controlled by a new debugfs
file, ib_check. All ib checking is off (0) by default,
because parsing and mem_entry lookup can have a performance
impact on some benchmarks. Level 1 checking verifies the
IB1's. Level 2 checking also verifies the IB2.