Apply bad098d76835 to 6.6.y and 6.7.y

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