pinctrl: abx500: get rid of unused variable

commit 2fcea6ce
"pinctrl: remove remaining users of gpiochip_remove() retval"
removed the use of the return value from gpiochip_remove()
but missed to delete the dangling "err" variable:

drivers/pinctrl/nomadik/pinctrl-abx500.c:
In function 'abx500_gpio_probe':
drivers/pinctrl/nomadik/pinctrl-abx500.c:1208:11:
warning: unused variable 'err' [-Wunused-variable]

Fix this by getting rid of the dangling variable.

Reported-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>