rename symbol: CONFIG_STM32 -> CONFIG_ARCH_STM32

Have this symbol follow the pattern of all other such symbols.

Signed-off-by: Trevor Woerner <twoerner@gmail.com>
diff --git a/drivers/gpio/Kconfig b/drivers/gpio/Kconfig
index 2081520..d87f6cc 100644
--- a/drivers/gpio/Kconfig
+++ b/drivers/gpio/Kconfig
@@ -318,7 +318,7 @@
 
 config STM32_GPIO
 	bool "ST STM32 GPIO driver"
-	depends on DM_GPIO && (STM32 || ARCH_STM32MP)
+	depends on DM_GPIO && (ARCH_STM32 || ARCH_STM32MP)
 	default y
 	help
 	  Device model driver support for STM32 GPIO controller. It should be