drm/amdgpu: Move fence SW fallback warning v3

Only print the warning if there was actually some fence processed
from the SW fallback timer.

v2: Add return value to amdgpu_fence_process to let
amdgpu_fence_fallback know fences were actually
processed and then print the warning.

v3: Always return true if seq != last_seq

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