Generated bitfield code triggers clippy `ptr_offset_of_cast` lint

This is an example of the output from clippy.

warning: use of `offset` with a `usize` casted to an `isize`
  --> /builds/bonzini/qemu/rust/target/debug/build/qemu_api-35cb647f4db404b8/out/bindings.inc.rs:39:21
   |
39 |         let byte = *(core::ptr::addr_of!((*this).storage) as *const u8).offset(byte_index as isize);
   |                     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `(core::ptr::addr_of!((*this).storage) as *const u8).add(byte_index)`
   |
   = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#ptr_offset_with_cast 
   = note: `#[warn(clippy::ptr_offset_with_cast)]` on by default
warning: use of `offset` with a `usize` casted to an `isize`
  --> /builds/bonzini/qemu/rust/target/debug/build/qemu_api-35cb647f4db404b8/out/bindings.inc.rs:68:13
   |
68 |             (core::ptr::addr_of_mut!((*this).storage) as *mut u8).offset(byte_index as isize);
   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `(core::ptr::addr_of_mut!((*this).storage) as *mut u8).add(byte_index)`
   |
   = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#ptr_offset_with_cast

The lint is enabled by default at "warn" level.

Start with the generated bindings.inc.rs locations shown in the clippy output, especially lines 39 and 68, and trace how this code is produced. Verify the generated bitfield code no longer emits the ptr_offset_with_cast warning when clippy runs.