build: Fix beta clippy issue (derive_partial_eq_without_eq)

warning: you are deriving `PartialEq` and can implement `Eq`
  --> vmm/src/serial_manager.rs:59:30
   |
59 | #[derive(Debug, Clone, Copy, PartialEq)]
   |                              ^^^^^^^^^ help: consider deriving `Eq` as well: `PartialEq, Eq`
   |
   = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#derive_partial_eq_without_eq

Signed-off-by: Rob Bradford <robert.bradford@intel.com>

tests/integration.rs

@@ -1614,7 +1614,7 @@ fn process_rss_kib(pid: u32) -> usize {
 // 10MB is our maximum accepted overhead.
 const MAXIMUM_VMM_OVERHEAD_KB: u32 = 10 * 1024;
 
-#[derive(PartialEq, PartialOrd)]
+#[derive(PartialEq, Eq, PartialOrd)]
 struct Counters {
     rx_bytes: u64,
     rx_frames: u64,