msm: kgsl: Add memfree_history debug feature

A kgsl user can free up an allocation of GPU memory with
kgsl_ioctl_sharedmem_free() function, but the GPU address
might still be in use resulting in a GPU page fault.
A bug of this kind is hard to find because the driver keeps
no trace of kgsl_ioctl_sharedmem_free calls.
This change implements a "memfree history" debug feture that
allows to see an information about a last couple of hundred
memory free calls in kernel/debug/kgsl/kgsl-3d0/memfree_history
file.

Change-Id: I12e0e3702db56d99d5de644739b364dea4cc37b1
Signed-off-by: Vladimir Razgulin <vrazguli@codeaurora.org>