arm64: Kconfig.platforms: Enable STM32_EXTI for ARCH_STM32

ARCH_STM32 needs to use STM32 EXTI interrupt controller for GPIO and wakeup
interrupts.
Signed-off-by: Antonio Borneo <antonio.borneo@foss.st.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20240415134926.1254428-8-antonio.borneo@foss.st.com

arch/arm64/Kconfig.platforms

@@ -302,6 +302,7 @@ config ARCH_STM32
 	select GPIOLIB
 	select PINCTRL
 	select PINCTRL_STM32MP257
+	select STM32_EXTI
 	select ARM_SMC_MBOX
 	select ARM_SCMI_PROTOCOL
 	select COMMON_CLK_SCMI