pinctrl: keembay: fix double free in keembay_build_functions()

This kfree() was accidentally left over when we converted to devm_
and it would lead to a double free.  Delete it.

Fixes: 995bc9f4826e ("pinctrl: keembay: release allocated memory in detach path")
Signed-off-by: Dan Carpenter <dan.carpenter@linaro.org>
Reviewed-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>