rust: sync: Replace `kernel::c_str!` with C-Strings

rust: sync: Replace `kernel::c_str!` with C-Strings

C-String literals were added in Rust 1.77. Replace instances of
`kernel::c_str!` with C-String literals where possible.

Signed-off-by: Tamir Duberstein <tamird@kernel.org>
Signed-off-by: Boqun Feng <boqun.feng@gmail.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Gary Guo <gary@garyguo.net>
Link: https://patch.msgid.link/20260120-cstr-sync-again-v1-1-2a775a2a36fd@kernel.org
Link: https://patch.msgid.link/20260123054624.8226-2-boqun.feng@gmail.com