fix incorrect kconfig default value of false, should be n

Author: olalonde

drivers/modem/Kconfig.cellular

@@ -65,6 +65,6 @@ config MODEM_CELLULAR_NEW_BAUDRATE_DELAY
 config MODEM_CELLULAR_POWER_ON_GNSS
 	bool "Power on the modem's GNSS module"
 	depends on DT_HAS_SIMCOM_A76XX_ENABLED
-	default false
+	default n
 
 endif