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

The i.MX pinctrl driver completely bails out when it detects an error
in the pinctrl nodes. This usually means that whatever error a
devicetree has the user is left blind because even the console cannot
be initialized without working pinmux.

Instead of bailing out completely, just continue probing. This makes
the pinctrl driver work, only the erroneous groups will fail later
during pin request time.

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>