drm/amdgpu: use new asic need_full_reset callback

Use the new callback to determine whether to use full
asic reset or per IP soft reset.  Enables reset to
actually proceed on asics which don't support soft
reset yet.

Reviewed-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Huang Rui <ray.huang@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>