drm/amdgpu: retry init if exclusive mode request is failed

This is caused of that hypervisor fails to handle request, one known
issue is MMIO unblocking timeout. In theory we can retry init here.
Signed-off-by: Npding <Pixel.Ding@amd.com>
Reviewed-by: NXiangliang Yu <Xiangliang.Yu@amd.com>
Signed-off-by: NAlex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/amdgpu/amdgpu_device.c

@@ -1625,7 +1625,7 @@ static int amdgpu_early_init(struct amdgpu_device *adev)
 	if (amdgpu_sriov_vf(adev)) {
 		r = amdgpu_virt_request_full_gpu(adev, true);
 		if (r)
-			return r;
+			return -EAGAIN;
 	}
 
 	for (i = 0; i < adev->num_ip_blocks; i++) {