drm/amdgpu: Set adev->vcn.irq.num_types for VCN

We were setting adev->uvd.irq.num_types instead.

Fixes: 9b257116 ("drm/amdgpu: add vcn enc irq support")
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Michel Dänzer <michel.daenzer@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Cc: stable@vger.kernel.org