Fixed wrong stack size start

Author: Andreas Larsson

targets/TARGET_STM/TARGET_STM32F4/TARGET_STM32F439xI/device/TOOLCHAIN_ARM_MICRO/startup_stm32f439xx.s

@@ -51,7 +51,7 @@ Stack_Size      EQU     0x00000400
                 EXPORT  __initial_sp
                 
 Stack_Mem       SPACE   Stack_Size
-__initial_sp    EQU     0x20020000 ; Top of RAM
+__initial_sp    EQU     0x20030000 ; Top of RAM
 
 
 ; <h> Heap Configuration