drm/amdgpu: simplify the return expression of iceland_ih_hw_init

Simplify the return expression.

Reported-by: Zeal Robot <zealci@zte.com.cn>
Signed-off-by: Minghao Chi <chi.minghao@zte.com.cn>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>