Async UART TX support

examples/simple/examples/spi.rs

@@ -59,7 +59,7 @@ fn main() -> ! {
     let spia_ref: RefCell<Option<SpiBase<pac::Spia, u8>>> = RefCell::new(None);
     let spib_ref: RefCell<Option<SpiBase<pac::Spib, u8>>> = RefCell::new(None);
     let pinsa = PinsA::new(&mut dp.sysconfig, dp.porta);
-    let pinsb = PinsB::new(&mut dp.sysconfig,  dp.portb);
+    let pinsb = PinsB::new(&mut dp.sysconfig, dp.portb);
 
     let mut spi_cfg = spi::SpiConfig::default();
     if EXAMPLE_SEL == ExampleSelect::Loopback {