rust: pin-init: allow pub fields in derive(Zeroable)

Add support for parsing `pub`, `pub(crate)` and `pub(super)` to the
derive macro `Zeroable`.

Link: Rust-for-Linux/pin-init@e8311e5
Signed-off-by: Benno Lossin <benno.lossin@proton.me>

Author: BennoLossin

rust/pin-init/src/macros.rs

@@ -1393,7 +1393,7 @@ macro_rules! __derive_zeroable {
         @body({
             $(
                 $(#[$($field_attr:tt)*])*
-                $field:ident : $field_ty:ty
+                $field_vis:vis $field:ident : $field_ty:ty
             ),* $(,)?
         }),
     ) => {