pinctrl: madera: Add missing call to pinctrl_unregister_mappings

pinctrl_register_mappings is called in the pdata case, however a call to
pinctrl_unregister_mappings is missing causing the mappings to be leaked
on driver unbind. Add the missing call to correct this issue.

Signed-off-by: Charles Keepax <ckeepax@opensource.cirrus.com>
Link: https://lore.kernel.org/r/20200228154214.13916-1-ckeepax@opensource.cirrus.com


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