vmm: Address Rust 1.51.0 clippy issue (upper_case_acroynms)

warning: name `ConvertFromUTF8` contains a capitalized acronym
  --> virtio-devices/src/vsock/unix/mod.rs:32:5
   |
32 |     ConvertFromUTF8(std::str::Utf8Error),
   |     ^^^^^^^^^^^^^^^ help: consider making the acronym lowercase, except the initial letter: `ConvertFromUtf8`
   |
   = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#upper_case_acronyms

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

virtio-devices/src/net_util.rs

@@ -69,7 +69,7 @@ unsafe impl ByteValued for VirtioNetConfig {}
 #[derive(Debug)]
 pub enum Error {
     /// Read process MQ.
-    FailedProcessMQ,
+    FailedProcessMq,
     /// Read queue failed.
     GuestMemory(GuestMemoryError),
     /// Invalid ctrl class
@@ -148,7 +148,7 @@ impl CtrlVirtio {
                         return Err(Error::InvalidCtlCmd);
                     }
                     if let Err(_e) = self.process_mq(&mem, avail_desc) {
-                        return Err(Error::FailedProcessMQ);
+                        return Err(Error::FailedProcessMq);
                     }
                 }
                 _ => return Err(Error::InvalidCtlClass),

virtio-devices/src/vsock/unix/mod.rs

@@ -29,7 +29,7 @@ mod defs {
 #[derive(Debug)]
 pub enum Error {
     /// Error converting from UTF-8
-    ConvertFromUTF8(std::str::Utf8Error),
+    ConvertFromUtf8(std::str::Utf8Error),
     /// Error registering a new epoll-listening FD.
     EpollAdd(std::io::Error),
     /// Error creating an epoll FD.

virtio-devices/src/vsock/unix/muxer.rs

@@ -474,7 +474,7 @@ impl VsockMuxer {
         }
 
         let mut word_iter = std::str::from_utf8(&buf[..blen])
-            .map_err(Error::ConvertFromUTF8)?
+            .map_err(Error::ConvertFromUtf8)?
             .split_whitespace();
 
         word_iter