samples: hello_world: Use full board target string for hwmv2 boards

Outputs the full board target string (including qualifiers) when
using a hwmv2 board

Signed-off-by: Jamie McCrae <jamie.mccrae@nordicsemi.no>

samples/hello_world/src/main.c

@@ -8,6 +8,7 @@
 
 int main(void)
 {
-	printf("Hello World! %s\n", CONFIG_BOARD);
+	printf("Hello World! %s\n", CONFIG_BOARD_TARGET);
+
 	return 0;
 }