sound: Fix some clippy lints

Fix cases where Self can be used in a type method, and remove enum
variant glob imports.

Signed-off-by: Manos Pitsidianakis <manos.pitsidianakis@linaro.org>

staging/vhost-device-sound/src/main.rs

@@ -24,7 +24,7 @@ impl TryFrom<SoundArgs> for SoundConfig {
     fn try_from(cmd_args: SoundArgs) -> Result<Self> {
         let socket = cmd_args.socket.trim().to_string();
 
-        Ok(SoundConfig::new(socket, false, cmd_args.backend))
+        Ok(Self::new(socket, false, cmd_args.backend))
     }
 }
 
@@ -46,7 +46,7 @@ mod tests {
 
     impl SoundArgs {
         fn from_args(socket: &str) -> Self {
-            SoundArgs {
+            Self {
                 socket: socket.to_string(),
                 backend: BackendType::default(),
             }

staging/vhost-device-sound/src/stream.rs

@@ -146,7 +146,7 @@ impl PCMState {
 
 impl std::fmt::Display for PCMState {
     fn fmt(&self, fmt: &mut std::fmt::Formatter) -> std::fmt::Result {
-        use PCMState::*;
+        use PCMState::{Prepare, Release, SetParameters, Start, Stop};
         match *self {
             SetParameters => {
                 write!(fmt, "VIRTIO_SND_R_PCM_SET_PARAMS")