msm: kgsl: Separate function to detect last command in recovery

Make the code more readable by writing a separate function to
detect the end of last command that is assumed to be successfully
executed by the GPU

Change-Id: Icab1f4e563ea533c48aba9c57afb548501e19552
Signed-off-by: Shubhraprakash Das <sadas@codeaurora.org>