pinctrl: mvebu: fix checking for SoC specific controls

This patch fixes a minor bug (probably due to a typo) while checking
the SoC specific controls in mvebu_pinctrl_probe().

Acked-by: Sebastian Hesselbarth <sebastian.hesselbarth@gmail.com>
Signed-off-by: Simon Guinot <simon.guinot@sequanux.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>