net/irda: sh_sir: tidyup compile warning

This patch tidyup below warning

${LINUX}/drivers/net/irda/sh_sir.c:514:6: warning:
 'val' may be used uninitialized in this function

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