add __weak for rt_hw_console_output (IAR)

git-svn-id: https://rt-thread.googlecode.com/svn/trunk@1172 bbd45198-f89e-11dd-88c7-29a3b14d5316

src/kservice.c

@@ -942,7 +942,7 @@ void rt_hw_console_output(const char* str)
 #elif defined(__CC_ARM)
 __weak void rt_hw_console_output(const char* str)
 #elif defined(__IAR_SYSTEMS_ICC__)
-void rt_hw_console_output(const char* str)
+__weak void rt_hw_console_output(const char* str)
 #endif
 {
     /* empty console output */