pinctrl: imxl: Fix an error handling path in 'imx1_pinctrl_core_probe()'

When 'pinctrl_register()' has been turned into 'devm_pinctrl_register()',
an error handling path has not been updated.

Axe a now unneeded 'pinctrl_unregister()'.

Fixes: e55e025d ("pinctrl: imxl: Use devm_pinctrl_register() for pinctrl registration")
Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Link: https://lore.kernel.org/r/20200530201952.585798-1-christophe.jaillet@wanadoo.fr


Signed-off-by: Linus Walleij <linus.walleij@linaro.org>