amdgpu: use amdgpu_gem_wait_idle_ioctl to wait for GPU to finish.

amdgpu: use amdgpu_gem_wait_idle_ioctl to wait for GPU to finish.

For linear path we don't wait for GPU to finish before CPU access
which may case issues in gralloc lock() case.

Bug=b:115585732
TEST=android.video.cts.VideoEncoderDecoderTest#testAvcGoog0Qual1920x1080

Change-Id: If827fe4a18726797082046b4f24fc8c75ff1bcb7
Signed-off-by: Deepak Sharma <Deepak.sharma@amd.com>
Reviewed-on: https://chromium-review.googlesource.com/1340484
Commit-Ready: Deepak Sharma <deepak.sharma@amd.com>
Tested-by: Deepak Sharma <deepak.sharma@amd.com>
Reviewed-by: Deepak Sharma <deepak.sharma@amd.com>
Reviewed-by: Gurchetan Singh <gurchetansingh@chromium.org>