rust: init: simplify from map_err to inspect_err

A new complexity lint, `manual_inspect` [1], has been introduced in
the upcoming Rust 1.81 (currently in nightly), which checks for uses of
`map*` which return the original item:

    error:
    --> rust/kernel/init.rs:846:23
        |
    846 |         (self.1)(val).map_err(|e| {
        |                       ^^^^^^^
        |
        = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#manual_inspect
        = note: `-D clippy::manual-inspect` implied by `-D warnings`
        = help: to override `-D warnings` add `#[allow(clippy::manual_inspect)]`
    help: try
        |
    846 ~         (self.1)(val).inspect_err(|e| {
    847 |             // SAFETY: `slot` was initialized above.
    848 ~             unsafe { core::ptr::drop_in_place(slot) };
        |

Thus clean them up.

Link: https://rust-lang.github.io/rust-clippy/master/index.html#/manual_inspect [1]
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>

rust/kernel/init.rs

@@ -843,11 +843,9 @@ where
  let val = unsafe { &mut *slot };
  // SAFETY: `slot` is considered pinned.
  let val = unsafe { Pin::new_unchecked(val) };
- (self.1)(val).map_err(|e| {
+ (self.1)(val).inspect_err(|_|
  // SAFETY: `slot` was initialized above.
- unsafe { core::ptr::drop_in_place(slot) };
- e
- })
+ unsafe { core::ptr::drop_in_place(slot) })
  }
 }
 
@@ -941,11 +939,9 @@ where
  // SAFETY: All requirements fulfilled since this function is `__init`.
  unsafe { self.0.__pinned_init(slot)? };
  // SAFETY: The above call initialized `slot` and we still have unique access.
- (self.1)(unsafe { &mut *slot }).map_err(|e| {
+ (self.1)(unsafe { &mut *slot }).inspect_err(|_|
  // SAFETY: `slot` was initialized above.
- unsafe { core::ptr::drop_in_place(slot) };
- e
- })
+ unsafe { core::ptr::drop_in_place(slot) })
  }
 }