drm/amdgpu: update the handle ptr in prepare_suspend

Update the *handle to amdgpu_ip_block ptr for all
functions pointers of prepare_suspend.

Signed-off-by: Sunil Khatri <sunil.khatri@amd.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>