ASoC: fsi: remove unused irq

FSI is using devm_request_irq() from
1ddd8286


(ASoC: fsi: use devm_request_irq())

master->irq is no longer needed.

Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>