pinctrl: mxs: do not export mxs_pinctrl_probe

No user of mxs_pinctrl_probe() can be built as a module, hence
exporting the symbol is not necessary. Drop EXPORT_SYMBOL_GPL.

Inspired by a patch from Stefan Agner for the tegra pinctrl driver.

Signed-off-by: Fabio Estevam <fabio.estevam@nxp.com>
Reviewed-by: Stefan Agner <stefan@agner.ch>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

drivers/pinctrl/freescale/pinctrl-mxs.c

@@ -556,4 +556,3 @@ err:
 	iounmap(d->base);
 	return ret;
 }
-EXPORT_SYMBOL_GPL(mxs_pinctrl_probe);