Add debugger asm::wfi workaround

Author: Sh3Rm4n

examples/serial_dma.rs

@@ -21,6 +21,15 @@ fn main() -> ! {
     let dp = pac::Peripherals::take().unwrap();
 
     let mut flash = dp.FLASH.constrain();
+
+    // https://github.com/probe-rs/probe-rs/issues/350#issuecomment-740550519
+    dp.DBGMCU.cr.modify(|_, w| {
+        w.dbg_sleep().set_bit();
+        w.dbg_standby().set_bit();
+        w.dbg_stop().set_bit()
+    });
+    dp.RCC.ahbenr.modify(|_, w| w.dma1en().enabled());
+
     let mut rcc = dp.RCC.constrain();
     let clocks = rcc.cfgr.freeze(&mut flash.acr);