rust: cpu: Add __rust_helper to helpers

This is needed to inline these helpers into Rust code.

Reviewed-by: Boqun Feng <[email protected]>
Reviewed-by: Gary Guo <[email protected]>
Signed-off-by: Alice Ryhl <[email protected]>
Signed-off-by: Boqun Feng <[email protected]>
Link: https://patch.msgid.link/[email protected]

rust/helpers/cpu.c

@@ -2,7 +2,7 @@
 
 #include <linux/smp.h>
 
-unsigned int rust_helper_raw_smp_processor_id(void)
+__rust_helper unsigned int rust_helper_raw_smp_processor_id(void)
 {
 	return raw_smp_processor_id();
 }