efi_driver: fix efi_uc_stop()

We must always call EFI_EXIT() when returning from an EFIAPI function.

Fixes: 05ef48a2 ("efi_driver: EFI block driver")
Signed-off-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>
Reviewed-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>

lib/efi_driver/efi_uclass.c

@@ -225,9 +225,10 @@ static efi_status_t EFIAPI efi_uc_stop(
 			ret = disconnect_child(controller_handle,
 					       child_handle_buffer[i]);
 			if (ret != EFI_SUCCESS)
-				return ret;
+				goto out;
 		}
-		return EFI_SUCCESS;
+		ret = EFI_SUCCESS;
+			goto out;
 	}
 
 	/* Destroy all children */