msm: kgsl: Protect fault detect start with active count

Get the active count when enabling GFT from sysfs so the performance
counters can be properly programmed.

CRs-Fixed: 622252
Change-Id: Ic0dedbadfe56f8c66aca15fb521494a2fc00332b
Signed-off-by: Jordan Crouse <jcrouse@codeaurora.org>