Revert "msm: kgsl: Add event to complete context detachment"

Revert commit 8963ea2d as a
dependent patch of 3a511817
which is being removed due to race conditions and stability
issues during device close.

Change-Id: Ic0dedbad3546fa393e9e73fd6f39e5b9678144cb
CRs-Fixed: 718284
Signed-off-by: Jordan Crouse <jcrouse@codeaurora.org>