scmi: add missing lifetime

rustc 1.83.0 (90b35a623 2024-11-26) emits 2 new warnings:

    warning: elided lifetime has a name
      --> vhost-device-scmi/src/devices/common.rs:69:60
       |
    69 |     fn extra<'a>(&'a self, allowed: &[&'a str]) -> HashSet<&str> {
       |              -- lifetime `'a` declared here                ^ this elided lifetime gets resolved as `'a`
       |
       = note: `#[warn(elided_named_lifetimes)]` on by default

    warning: elided lifetime has a name
      --> vhost-device-scmi/src/devices/common.rs:74:63
       |
    74 |     fn missing<'a>(&'a self, required: &[&'a str]) -> HashSet<&str> {
       |                -- lifetime `'a` declared here                 ^ this elided lifetime gets resolved as `'a`

    warning: `vhost-device-scmi` (bin "vhost-device-scmi") generated 2 warnings

Fixes: rust-vmm#786
Signed-off-by: Stefano Garzarella <[email protected]>

vhost-device-scmi/src/devices/common.rs

@@ -66,12 +66,12 @@ impl DeviceProperties {
         self.0.iter().map(|(n, _)| -> &str { n.as_str() }).collect()
     }
 
-    fn extra<'a>(&'a self, allowed: &[&'a str]) -> HashSet<&str> {
+    fn extra<'a>(&'a self, allowed: &[&'a str]) -> HashSet<&'a str> {
         let allowed_set: HashSet<&str> = HashSet::from_iter(allowed.iter().copied());
         self.names().difference(&allowed_set).copied().collect()
     }
 
-    fn missing<'a>(&'a self, required: &[&'a str]) -> HashSet<&str> {
+    fn missing<'a>(&'a self, required: &[&'a str]) -> HashSet<&'a str> {
         let required_set: HashSet<&str> = HashSet::from_iter(required.iter().copied());
         required_set.difference(&self.names()).copied().collect()
     }