drm/amdgpu: read and authenticate ip discovery binary

read and authenticate ip discovery binary getting from
vram first, if it is not valid, read and authenticate
the one getting from file

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