ASoC: stm32: sai: clean up indentation issue

There is a statement that is indented one level too deeply,
remove the extraneous tab.
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Link: https://lore.kernel.org/r/20190925112621.9312-1-colin.king@canonical.comSigned-off-by: Mark Brown <broonie@kernel.org>