ASoC: kirkwood-i2s: fix error return code in kirkwood_i2s_dev_probe()

platform_get_irq() returns an error code, but the kirkwood-i2s
driver ignores it and always returns -ENXIO. This is not correct,
and prevents -EPROBE_DEFER from being propagated properly.
Notice that platform_get_irq() no longer returns 0 on error.

Print and propagate the return value of platform_get_irq on failure.

Signed-off-by: Gustavo A. R. Silva <garsilva@embeddedor.com>
Signed-off-by: Mark Brown <broonie@kernel.org>