Remove SystemInit() that was used by newlib

Author: voltur01

samples/src/baremetal-semihosting/hello.c

@@ -4,5 +4,3 @@ int main(void) {
   printf("Hello World!\n");
   return 0;
 }
-
-void SystemInit() {}

samples/src/cpp-baremetal-semihosting/hello.cpp

@@ -13,7 +13,3 @@ int main(void) {
 
   return 0;
 }
-
-extern "C" {
-void SystemInit() {}
-}