rust: jump_label: add __rust_helper to helpers

This is needed to inline these helpers into Rust code.

Reviewed-by: Boqun Feng <boqun.feng@gmail.com>
Reviewed-by: Gary Guo <gary@garyguo.net>
Signed-off-by: Alice Ryhl <aliceryhl@google.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://patch.msgid.link/20260105-define-rust-helper-v2-9-51da5f454a67@google.com
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>

rust/helpers/jump_label.c

@@ -7,7 +7,7 @@
 #include <linux/jump_label.h>
 
 #ifndef CONFIG_JUMP_LABEL
-int rust_helper_static_key_count(struct static_key *key)
+__rust_helper int rust_helper_static_key_count(struct static_key *key)
 {
 	return static_key_count(key);
 }