clippy: Fix redundant allocations

With the new beta version, clippy complains about redundant allocation
when using Arc<Box<dyn T>>, and suggests replacing it simply with
Arc<dyn T>.

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

pci/src/msix.rs

@@ -74,7 +74,7 @@ pub struct MsixConfig {
     pub table_entries: Vec<MsixTableEntry>,
     pub pba_entries: Vec<u64>,
     pub devid: u32,
-    interrupt_source_group: Arc<Box<dyn InterruptSourceGroup>>,
+    interrupt_source_group: Arc<dyn InterruptSourceGroup>,
     masked: bool,
     enabled: bool,
 }
@@ -82,7 +82,7 @@ pub struct MsixConfig {
 impl MsixConfig {
     pub fn new(
         msix_vectors: u16,
-        interrupt_source_group: Arc<Box<dyn InterruptSourceGroup>>,
+        interrupt_source_group: Arc<dyn InterruptSourceGroup>,
         devid: u32,
     ) -> Self {
         assert!(msix_vectors <= MAX_MSIX_VECTORS_PER_DEVICE);