pinctrl: sx150x: Unregister the pinctrl on release

commit 0657cb50b5a75abd92956028727dc255d690a4a6 upstream.

There is no matching call to pinctrl_unregister, so switch to the
managed devm_pinctrl_register to clean up properly when done.

Fixes: 9e80f906 ("pinctrl: Add SX150X GPIO Extender Pinctrl Driver")
Signed-off-by: Peter Rosin <peda@axentia.se>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>