drm/amdgpu: move amdgpu_device_get_job_timeout_settings

It's only used in amdgpu_device.c and the naming also
reflects that.  Move it there.

Reviewed-by: Andrey Grodzovsky <andrey.grodzovsky@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>