The AW9523 driver fails to build in some allmod configs since the
I2C core can be a module, but AW9523 can not. Fix it up by allowing
AW9523 to be a module (tristate).

Fixes: 576623d7 ("pinctrl: Add driver for Awinic AW9523/B I2C GPIO Expander")
Reported-by: Arnd Bergmann <arnd@arndb.de>
Reported-by: Geert Uytterhoeven <geert@linux-m68k.org>
Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202403050916.KBtE6eEj-lkp@intel.com/Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Link: https://lore.kernel.org/r/20240305-fix-aw9523-v2-1-2dc50bab2b17@linaro.org