ASoC: fsi: Add pr_err for noticing unsupported access

This patch didn't use dev_err,
because it is difficult to get struct device here.

Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Acked-by: Liam Girdwood <lrg@slimlogic.co.uk>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>