drm/amdgpu: clean up jpeg reset functions

Make them consistent and use the reset flags.

Reviewed-by: Sathishkumar S <sathishkumar.sundararaju@amd.com>
Acked-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>