linters: Fix clippy issues

Latest clippy version complains about our existing code for the
following reasons:

- trait objects without an explicit `dyn` are deprecated
- `...` range patterns are deprecated
- lint `clippy::const_static_lifetime` has been renamed to
  `clippy::redundant_static_lifetimes`
- unnecessary `unsafe` block
- unneeded return statement

All these issues have been fixed through this patch, and rustfmt has
been run to cleanup potential formatting errors due to those changes.

Signed-off-by: Sebastien Boeuf <sebastien.boeuf@intel.com>

devices/src/bus.rs

@@ -77,7 +77,7 @@ impl PartialOrd for BusRange {
 /// only restriction is that no two devices can overlap in this address space.
 #[derive(Clone, Default)]
 pub struct Bus {
-    devices: BTreeMap<BusRange, Arc<Mutex<BusDevice>>>,
+    devices: BTreeMap<BusRange, Arc<Mutex<dyn BusDevice>>>,
 }
 
 impl Bus {
@@ -88,7 +88,7 @@ impl Bus {
         }
     }
 
-    fn first_before(&self, addr: u64) -> Option<(BusRange, &Mutex<BusDevice>)> {
+    fn first_before(&self, addr: u64) -> Option<(BusRange, &Mutex<dyn BusDevice>)> {
         let (range, dev) = self
             .devices
             .range(..=BusRange { base: addr, len: 1 })
@@ -97,7 +97,7 @@ impl Bus {
         Some((*range, dev))
     }
 
-    pub fn resolve(&self, addr: u64) -> Option<(u64, u64, &Mutex<BusDevice>)> {
+    pub fn resolve(&self, addr: u64) -> Option<(u64, u64, &Mutex<dyn BusDevice>)> {
         if let Some((range, dev)) = self.first_before(addr) {
             let offset = addr - range.base;
             if offset < range.len {
@@ -108,7 +108,7 @@ impl Bus {
     }
 
     /// Puts the given device at the given address space.
-    pub fn insert(&mut self, device: Arc<Mutex<BusDevice>>, base: u64, len: u64) -> Result<()> {
+    pub fn insert(&mut self, device: Arc<Mutex<dyn BusDevice>>, base: u64, len: u64) -> Result<()> {
         if len == 0 {
             return Err(Error::Overlap);
         }