[VK_RZ_A1H] Maked __iar_program_start as weak

Author: geky

hal/targets/cmsis/TARGET_RENESAS/TARGET_VK_RZ_A1H/TOOLCHAIN_IAR/startup_VKRZA1H.s

@@ -30,7 +30,7 @@
         SECTION .intvec:CODE:NOROOT(2)
 
         PUBLIC  __vector
-        PUBLIC  __iar_program_start
+        PUBWEAK __iar_program_start
         PUBLIC  Undefined_Handler
         EXTERN  SWI_Handler
         PUBLIC  Prefetch_Handler