STM32F103xE: correct GCC startup file

Author: jeromecoutant

targets/TARGET_STM/TARGET_STM32F1/TARGET_STM32F103xE/TOOLCHAIN_GCC_ARM/startup_stm32f103xe.S

@@ -93,10 +93,8 @@ LoopFillZerobss:
 
 /* Call the clock system intitialization function.*/
     bl  SystemInit
-/* Call static constructors */
-    bl __libc_init_array
-/* Call the application's entry point.*/
-  bl main
+	bl _start
+	bx lr
   bx lr
 .size Reset_Handler, .-Reset_Handler