net_util: queue_pair: Remove unnecessary mut from reference

warning: this argument is a mutable reference, but not used mutably
   --> net_util/src/queue_pair.rs:167:14
    |
167 |         tap: &mut Tap,
    |              ^^^^^^^^ help: consider changing to: `&Tap`
    |
    = warning: changing this function will impact semver compatibility
    = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#needless_pass_by_ref_mut

Signed-off-by: Rob Bradford <rbradford@rivosinc.com>

net_util/src/queue_pair.rs

@@ -38,7 +38,7 @@ impl TxVirtio {
     pub fn process_desc_chain(
         &mut self,
         mem: &GuestMemoryMmap,
-        tap: &mut Tap,
+        tap: &Tap,
         queue: &mut Queue,
         rate_limiter: &mut Option<RateLimiter>,
         access_platform: Option<&Arc<dyn AccessPlatform>>,
@@ -164,7 +164,7 @@ impl RxVirtio {
     pub fn process_desc_chain(
         &mut self,
         mem: &GuestMemoryMmap,
-        tap: &mut Tap,
+        tap: &Tap,
         queue: &mut Queue,
         rate_limiter: &mut Option<RateLimiter>,
         access_platform: Option<&Arc<dyn AccessPlatform>>,
@@ -357,7 +357,7 @@ impl NetQueuePair {
     ) -> Result<bool, NetQueuePairError> {
         let tx_tap_retry = self.tx.process_desc_chain(
             mem,
-            &mut self.tap,
+            &self.tap,
             queue,
             &mut self.tx_rate_limiter,
             self.access_platform.as_ref(),
@@ -407,7 +407,7 @@ impl NetQueuePair {
     ) -> Result<bool, NetQueuePairError> {
         self.rx_desc_avail = !self.rx.process_desc_chain(
             mem,
-            &mut self.tap,
+            &self.tap,
             queue,
             &mut self.rx_rate_limiter,
             self.access_platform.as_ref(),