ASoC: spear: fix error return code in spdif_in_probe()

platform_get_irq() returns an error code, but the spdif_in driver
ignores it and always returns -EINVAL. This is not correct, and
prevents -EPROBE_DEFER from being propagated properly.

Notice that platform_get_irq() no longer returns 0 on error:
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=e330b9a6



Print error message 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>