stm32l4: Cleanup examples

* Use `cortex_m_rt::entry` for sync examples
* Use `Dbgmcu::enable_all()` everywhere

examples/stm32l4/src/bin/button.rs

@@ -8,25 +8,21 @@
 
 #[path = "../example_common.rs"]
 mod example_common;
-use defmt::panic;
-use embassy::executor::Spawner;
+use embassy_stm32::dbgmcu::Dbgmcu;
 use embassy_stm32::gpio::{Input, Pull};
-use embassy_stm32::{pac, Peripherals};
 use embedded_hal::digital::v2::InputPin;
 use example_common::*;
 
-#[embassy::main]
-async fn main(_spawner: Spawner, p: Peripherals) {
+#[cortex_m_rt::entry]
+fn main() -> ! {
     info!("Hello World!");
 
     unsafe {
-        pac::DBGMCU.cr().modify(|w| {
-            w.set_dbg_sleep(true);
-            w.set_dbg_standby(true);
-            w.set_dbg_stop(true);
-        });
+        Dbgmcu::enable_all();
     }
 
+    let p = embassy_stm32::init(Default::default());
+
     let button = Input::new(p.PC13, Pull::Up);
 
     loop {