pinctrl/pinctrl-u300: remove unneeded devm_kfree call

the allocated memory will be destroyed at the driver unload time,
automatically if driver uses the devm_ functions, so no need of
doing devm_kfree at the error path

Signed-off-by: Devendra Naga <develkernel412222@gmail.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>