msm: kgsl: Clear OOB for CP init if HFI start fails

If the HFI start message fails, the outstanding OOB
must be cleared in the error path. If it does not get
cleared, the GMU will never idle on the way to slumber.

Change-Id: I242d8aac6def483999d35efc70bd6e23be1648dd
Signed-off-by: Kyle Piefer <kpiefer@codeaurora.org>