Apply rustfmt to the usb_serial example

Author: Disasm

examples/usb_serial.rs

@@ -6,15 +6,15 @@ extern crate panic_semihosting;
 
 use cortex_m_rt::entry;
 use stm32l0xx_hal::usb::{Peripheral, UsbBus};
-use stm32l0xx_hal::{prelude::*, pac, rcc};
+use stm32l0xx_hal::{pac, prelude::*, rcc};
 use usb_device::prelude::*;
 use usbd_serial::{SerialPort, USB_CLASS_CDC};
 
 #[entry]
 fn main() -> ! {
     let dp = pac::Peripherals::take().unwrap();
 
-    let mut rcc    = dp.RCC.freeze(rcc::Config::hsi16());
+    let mut rcc = dp.RCC.freeze(rcc::Config::hsi16());
 
     let gpioa = dp.GPIOA.split(&mut rcc);