pinctrl: at91: use devm_kasprintf() to avoid potential leaks

Use devm_kasprintf() instead of kasprintf() to avoid any potential
leaks. At the moment drivers have no remove functionality thus
there is no need for fixes tag.

Signed-off-by: Claudiu Beznea <claudiu.beznea@microchip.com>
Link: https://lore.kernel.org/r/20230203132714.1931596-1-claudiu.beznea@microchip.com


Signed-off-by: Linus Walleij <linus.walleij@linaro.org>