net/irda/sh_irda: return to RX mode when TX error

sh_irda can not use RX/TX in same time,
but this driver didn't return to RX mode when TX error occurred.
This patch care xmit error case to solve this issue.

Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Signed-off-by: David S. Miller <davem@davemloft.net>