Reexport NVIC_PRIO_BITS at HAL root.

This allows using RTIC with `#[rtic::app(device = embassy_nrf, ...)]`

embassy-nrf/src/chips/nrf5340_app.rs

@@ -5,6 +5,8 @@ pub mod pac {
     // The nRF5340 has a secure and non-secure (NS) mode.
     // To avoid cfg spam, we remove _ns or _s suffixes here.
 
+    pub use nrf5340_app_pac::NVIC_PRIO_BITS;
+    
     #[doc(no_inline)]
     pub use nrf5340_app_pac::{
         interrupt,