M2: msm: Enable IOMMU_GPU_SYNC

1. We need this to run with the new QdevNet adreno blobs.

2. HACK: prevent APPS side locking;  it's aggrevating the modem wdog.
Not sure why this happens, perhaps cpuidle, or preemption is
somehow responsible for the lock being held longer than anticipated.

3. Result is: serialized GPU-GPU acess to the context registers.
Apparently this is all that is needed to be able to use the QdevNet
adreno blobs.