drm/amd/amdgpu: enable clockgating only after late init

Sometimes during multiple reboots, the system hangs
during bootup. The issue is very random and happens
once in around 50 reboots or so.

It seems if clockgating is enabled before late init,
the GFX engine sometimes does not respond.

This patch changes the ordering a little so that
both powergating and clockgating are enabled only
after late init calls.

Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Arindam Nath <arindam.nath@amd.com>
Tested-by: Sunil Uttarwar <Sunil.Uttarwar1@amd.com>
Reviewed-by: Tom St Denis <tom.stdenis@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>