msm: kgsl: Wait for active count when last kgsl instance is closed

Move the wait one level up so that we wait for active count before
we call the target specific function to execute the last close.

Change-Id: I2e877cd9b66e37e4894789e22fa2fdabaf72ff96
Signed-off-by: Harshdeep Dhatt <hdhatt@codeaurora.org>