ASoC: fsl_sai: simplify irq return value

Instead of using a boolean "irq_none" to describe the interrupt
handlers return value use a variable of type irqreturn_t and return
it directly. No functional change.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
Link: https://lore.kernel.org/r/20220302083428.3804687-3-s.hauer@pengutronix.de


Signed-off-by: Mark Brown <broonie@kernel.org>