key: use c_long type for keyctl_search() helper fn

The keyctl_search() C function returns a long, which is already
reflected in the KeyHandle._id type. The search_keyring() helper
function currently returns a Result<i64>, which breaks 32-bit builds for
e.g. armv7l:
  error[E0308]: mismatched types
     --> src/key.rs:121:16
      |
  121 |             Ok(key_id)
      |             -- ^^^^^^ expected `i64`, found `i32`
      |             |
      |             arguments to this enum variant are incorrect
...
  error[E0308]: mismatched types
     --> src/key.rs:135:24
      |
  135 |                 _id:   id,
      |                        ^^ expected `i32`, found `i64`

Fix this by changing search_keyring() to return a Result<c_long>.

Fixes: f72ded6a ("fix(key): search for key in all relevant keyrings")
Signed-off-by: David Disseldorp <ddiss@suse.de>
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

src/key.rs

@@ -110,7 +110,7 @@ impl KeyHandle {
         }
     }
 
-    fn search_keyring(keyring: i32, key_name: &CStr) -> Result<i64> {
+    fn search_keyring(keyring: i32, key_name: &CStr) -> Result<c_long> {
         let key_name = CStr::as_ptr(key_name);
         let key_type = c_str!("user");