drm/amdgpu: introduce new request and its function

1) modify xgpu_nv_send_access_requests to support
new idh request

2) introduce new function: req_gpu_init_data() which
is used to notify host to prepare vbios/ip-discovery/pfvf exchange

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