Fix clippy warnings breaking the master build

[lshlyapnikov]

https://github.com/rust-lang/socket2/actions/runs/3759675926/jobs/6389525887

error: clamp-like pattern without using clamp function
   --> src/sys/unix.rs:650:5
    |
650 | /     if value <= min {
651 | |         min
652 | |     } else if value >= max {
653 | |         max
654 | |     } else {
655 | |         value
656 | |     }
    | |_____^ help: replace with clamp: `value.clamp(min, max)`
    |
    = note: clamp will panic if max < min
    = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#manual_clamp
    = note: `-D clippy::manual-clamp` implied by `-D warnings`

error: casting to the same type is unnecessary (`usize` -> `usize`)
   --> src/sys/unix.rs:785:38
    |
785 |     msg.msg_iovlen = min(bufs.len(), IovLen::MAX as usize) as IovLen;
    |                                      ^^^^^^^^^^^^^^^^^^^^ help: try: `IovLen::MAX`
    |
    = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#unnecessary_cast
    = note: `-D clippy::unnecessary-cast` implied by `-D warnings`

error: casting to the same type is unnecessary (`usize` -> `usize`)
   --> src/sys/unix.rs:845:38
    |
845 |     msg.msg_iovlen = min(bufs.len(), IovLen::MAX as usize) as IovLen;
    |                                      ^^^^^^^^^^^^^^^^^^^^ help: try: `IovLen::MAX`
    |
    = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#unnecessary_cast

error: clamp-like pattern without using clamp function
   --> src/sys/unix.rs:650:5
    |
650 | /     if value <= min {
651 | |         min
652 | |     } else if value >= max {
653 | |         max
654 | |     } else {
655 | |         value
656 | |     }
    | |_____^ help: replace with clamp: `value.clamp(min, max)`
    |
    = note: clamp will panic if max < min
    = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#manual_clamp
note: the lint level is defined here
   --> src/lib.rs:58:24
    |
58  | #![cfg_attr(test, deny(warnings))]
    |                        ^^^^^^^^
    = note: `#[deny(clippy::manual_clamp)]` implied by `#[deny(warnings)]`

error: casting to the same type is unnecessary (`usize` -> `usize`)
   --> src/sys/unix.rs:785:38
    |
785 |     msg.msg_iovlen = min(bufs.len(), IovLen::MAX as usize) as IovLen;
    |                                      ^^^^^^^^^^^^^^^^^^^^ help: try: `IovLen::MAX`
    |
    = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#unnecessary_cast
    = note: `#[deny(clippy::unnecessary_cast)]` implied by `#[deny(warnings)]`

error: could not compile `socket2` due to 3 previous errors
warning: build failed, waiting for other jobs to finish...
error: could not compile `socket2` due to 3 previous errors
Error: Process completed with exit code 101.