tests: gpio: add initial state of GPIO set bits
tests: gpio: add initial state of GPIO set bits

When a GPIO is 1 and port_set_bits_raw_and_verify function does
not set that bit, it will still be 1. So calculate the expected
value only by the parameter of port_set_bits_raw_and_verify is
not enough. A proper way is to clear all the GPIO bit fist and
then do the test.
Fixes: #49714

Signed-off-by: Hu Zhenyu <226749fd2157ff6d4888d78f2def87a906fe4d4a@intel.com>

zephyrproject-rtos/zephyr,galak/zephyr,finikorg/zephyr,galak/zephyr,finikorg/zephyr,finikorg/zephyr,finikorg/zephyr,galak/zephyr,zephyrproject-rtos/zephyr,finikorg/zephyr,zephyrproject-rtos/zephyr,galak/zephyr,zephyrproject-rtos/zephyr,galak/zephyr,zephyrproject-rtos/zephyr