added RTT example app

examples/rtt-log.rs

@@ -0,0 +1,19 @@
+//! Code to test RTT logger functionality
+#![no_main]
+#![no_std]
+
+use cortex_m_rt::entry;
+use panic_halt as _;
+use rtt_target::{rprintln, rtt_init_print};
+use va108xx as _;
+
+#[entry]
+fn main() -> ! {
+    rtt_init_print!();
+    let mut counter = 0;
+    loop {
+        rprintln!("{}: Hello, world!", counter);
+        counter += 1;
+        cortex_m::asm::delay(25_000_000);
+    }
+}