boards: arm: mimimxrt685_evk_cm33: workaround to support sys_reboot

On the RT685, the sys_reboot API does not function correctly. This is
due to the fact that the external flash must be reset at power on. In
order to configure the ROM to reset the flash, a OTP shadow register
can be programmed with the GPIO port and pin of the flash reset pin.

Program these bits at boot when the CONFIG_REBOOT symbol is set,
so that sys_reboot works as expected.

Signed-off-by: Daniel DeGrasse <daniel.degrasse@nxp.com>