gpiolib: Get rid of devprop prefix in one function

The devprop prefix in the devprop_gpiochip_set_names() adds confusion.
Get rid of it.

Note we have more than one function in the same module that handles
one or more device properties. This change will unify the naming schema
for all of them.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>