drm/amdgpu/psp: move psp version specific function pointers to early_init

In case we need to use them for GPU reset prior initializing the
asic.  Fixes a crash if the driver attempts to reset the GPU at driver
load time.

Acked-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Cc: stable@vger.kernel.org