Avoid a gpiochip_free() and use standard functions.

Cc: John Crispin <blogic@openwrt.org>
Cc: Pramod Gurav <pramod.gurav@smartplayin.com>
Cc: Martin Schiller <mschiller@tdt.de>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>