gpio: wcove: use regmap_assign_bits() in .set()

gpio: wcove: use regmap_assign_bits() in .set()

Replace the if-else with a direct call to the regmap_assign_bits()
helper and save a couple lines of code.

Reviewed-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/20250715-gpiochip-set-rv-gpio-remaining-v2-1-072b4cf06330@linaro.org
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>