drm/amdgpu: add helper to execute atomfirmware asic_init

Add helper function to execute atomfirmware asic_init
from the cmd table

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