Bindgen generates unnecessary unsafe blocks

[wintermelons]

After a502187, ::std::mem::transmute(val) are changed to val as _, but the outer unsafe blocks are still generated, resulting in build errors like

error: unnecessary `unsafe` block
     --> ../../src/starnix/lib/linux_uapi/src/x86_64.rs:12344:9
      |
12344 |         unsafe {
      |         ^^^^^^ unnecessary `unsafe` block