vm-allicator: Remove "new_without_default" clippy

Add a Default implementation that delegates to new, so that clippy
can be removed.

Signed-off-by: Ravi kumar Veeramally <ravikumar.veeramally@intel.com>

vm-allocator/src/gsi.rs

@@ -63,7 +63,6 @@ impl GsiAllocator {
     }
 
     #[cfg(target_arch = "aarch64")]
-    #[allow(clippy::new_without_default)]
     /// New GSI allocator
     pub fn new() -> Self {
         GsiAllocator {
@@ -106,3 +105,10 @@ impl GsiAllocator {
         Ok(irq)
     }
 }
+
+#[cfg(target_arch = "aarch64")]
+impl Default for GsiAllocator {
+    fn default() -> Self {
+        GsiAllocator::new()
+    }
+}