drm/amdgpu/jpeg: fix jpeg_v5_0_1_is_idle detection

drm/amdgpu/jpeg: fix jpeg_v5_0_1_is_idle detection

jpeg_v5_0_1_is_idle() initializes ret to false and then accumulates ring
idle status using &=. Since false & condition always remains false, the
function can never report the JPEG block as idle.

Initialize ret to true so the function returns true only when all JPEG
rings report RB_JOB_DONE.

Signed-off-by: Boyuan Zhang <boyuan.zhang@amd.com>
Reviewed-by: David (Ming Qiang) Wu <David.Wu3@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
(cherry picked from commit 680adf5faeeabb4585f7aeb53681719e2d6c2f41)
Cc: stable@vger.kernel.org