Apply bad098d76835 to 6.6.y and 6.7.y

[Miguel Ojeda <miguel.ojeda.sandonis@xxxxxxxxx>]

Hi Greg and Sasha,

Please consider applying commit bad098d76835 ("rust: Ignore
preserve-most functions") to 6.6.y and 6.7.y (6.1.y does not need it
since `__preserve_most` was introduced in 6.6). It fixes a build error
with Rust + `CONFIG_LIST_HARDENED`. It should apply cleanly.

Thanks!

Cheers,
Miguel