drm/amdgpu/gmc7: fix wait_for_idle callers

The wait_for_idle signature was changed, but the callers
were not.

Reviewed-by: Sunil Khatri <sunil.khatri@amd.com>
Reported-by: Michel Dänzer <michel@daenzer.net>
Fixes: 82ae6619 ("drm/amdgpu: update the handle ptr in wait_for_idle")
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Cc: Sunil Khatri <sunil.khatri@amd.com>