cxl: Reset default context for vPHB on release

When we release the device, we should also invalidate the default context.
With this cxl_get_context() will return null after removal.

Signed-off-by: Michael Neuling <mikey@neuling.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
diff --git a/drivers/misc/cxl/vphb.c b/drivers/misc/cxl/vphb.c
index f733309..b1d1983a 100644
--- a/drivers/misc/cxl/vphb.c
+++ b/drivers/misc/cxl/vphb.c
@@ -72,6 +72,7 @@
 			dev_err(&dev->dev, "Default context started\n");
 			return;
 		}
+		dev->dev.archdata.cxl_ctx = NULL;
 		cxl_release_context(ctx);
 	}
 }