drm/amdgpu: switch to atomfirmware_asic_init

Some initial settings now are not available from
the atom data table. The assumption that !ps[0]
|| !ps[1] in amdgpu_atom_asic_init is not valid.
In addition, driver needs to strictly follow
atomfirmware structure (asic_init_parameters) to
initialize parameters used to execute asic_init
function, otherwise, the execution of asic_init
would fail.

This shall be applicable to all soc15 adapters,but
let make the transition on soc21 first.

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>