dvb: don't use flush_scheduled_work()

flush_scheduled_work() is deprecated and scheduled to be removed.

* Flush the used works directly.

* Replace the deprecated cancel_rearming_delayed_work() +
  flush_scheduled_work() -> cancel_delayed_work_sync().

* Make sure mantis->uart_work isn't running on exit.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Mauro Carvalho Chehab <mchehab@infradead.org>
Cc: linux-media@vger.kernel.org
diff --git a/drivers/media/dvb/mantis/mantis_uart.c b/drivers/media/dvb/mantis/mantis_uart.c
index 7d2f239..97b889e 100644
--- a/drivers/media/dvb/mantis/mantis_uart.c
+++ b/drivers/media/dvb/mantis/mantis_uart.c
@@ -182,5 +182,6 @@
 {
 	/* disable interrupt */
 	mmwrite(mmread(MANTIS_UART_CTL) & 0xffef, MANTIS_UART_CTL);
+	flush_work_sync(&mantis->uart_work);
 }
 EXPORT_SYMBOL_GPL(mantis_uart_exit);