pinctrl: sunplus: Add check for kmalloc

Fix Smatch static checker warning:
potential null dereference 'configs'. (kmalloc returns null)

Fixes: aa74c44b ("pinctrl: Add driver for Sunplus SP7021")
Signed-off-by: Wells Lu <wellslutw@gmail.com>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Link: https://lore.kernel.org/r/1685277277-12209-1-git-send-email-wellslutw@gmail.com


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