Remove redundant extern SystemInit

Signed-off-by: NZbigniew Bodek <zbigniew.bodek@huawei.com>
Change-Id: I3c93fd703eb184d946f25a7f6be3c70124b469c1

kernel/common/los_config.c

@@ -130,7 +130,6 @@ extern "C" {
 #endif /* __cplusplus */
 
 extern UINT32 OsSystemInit(VOID);
-extern VOID SystemInit(VOID);
 
 VOID __attribute__((weak)) SystemInit(VOID)
 {