ASoC: meson: use IRQ_RETVAL in the fifo irq handler

Use IRQ_RETVAL instead of the open coded ternary operation.

Suggested-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Jerome Brunet <jbrunet@baylibre.com>
Signed-off-by: Mark Brown <broonie@kernel.org>