drm/amdgpu: remove virt_init_data_exchange from poison consumption handler

Host will initiate an FLR for all poison consumption.
Guest should wait for FLR message to re-init data exchange.

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