drm/amdgpu: add sdma2 and sdma3 irqsrc header files for sienna_cichlid (v2)

Add irq src headers for additional SDMA blocks.

v2: Add missing licenses (Alex)

Signed-off-by: Likun Gao <Likun.Gao@amd.com>
Reviewed-by: Hawking Zhang <Hawking.Zhang@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
