ASoC: fsl: fsl_spdif: No need to check the return value of platform_get_resource()

When using devm_ioremap_resource(), we do not need to check the return value of
platform_get_resource(), so just remove it.

Signed-off-by: Fabio Estevam <fabio.estevam@freescale.com>
Signed-off-by: Mark Brown <broonie@linaro.org>