pinctrl: imx: do not fail when parsing a function fails

When parsing a function fails this is no reason to make the whole
driver fail. Just continue with the next function.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
Acked-by: Shawn Guo <shawn.guo@linaro.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>