greybus: connection: export gb_connection_disable_rx() fn

gb_connection_disable_rx() fn is required to be used by other modules
(e.g. bridged-phy drivers) and so export it.

Testing Done: Tested on gbsim.
Signed-off-by: Vaibhav Hiremath <vaibhav.hiremath@linaro.org>
Reviewed-by: Viresh Kumar <viresh.kumar@linaro.org>
Tested-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>

drivers/staging/greybus/connection.c

@@ -617,6 +617,7 @@ void gb_connection_disable_rx(struct gb_connection *connection)
 out_unlock:
 	mutex_unlock(&connection->mutex);
 }
+EXPORT_SYMBOL_GPL(gb_connection_disable_rx);
 
 void gb_connection_disable(struct gb_connection *connection)
 {