drm/amdgpu: add autoload_supported check for RLC autoload

Asic cyan_skilfish2 won't support RLC autoload when using
front door loading. We just use PSP to load firmware like
gfx9 here.

So add autoload_supported flag check instead of just
checking firmware load type for RLC autoload.

Signed-off-by: Lang Yu <Lang.Yu@amd.com>
Reviewed-by: Huang Rui <ray.huang@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>