drm/amdgpu: Set ip_blocks according variable amdgpu_virtual_display.

For virtual display feature, if user set the option "amdgpu.virtual_display=1"
when load amdgpu.ko. Then need to set the ip_blocks with virtual display ip
blocks. And when enable virtual display, the amdgpu_dal need to be set to zero.

Signed-off-by: Emily Deng <Emily.Deng@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>