Use bits in impl_flags!'s example #1244

Update the impl_flags! example to use the bits module.

Please also consider whether it may be worth it to add these to the prelude (in a separate patch).

Lore: https://lore.kernel.org/rust-for-linux/CANiq72kxNx6wdvAW1DjGm=JhPiqs74qwxfPQ6cRHxiuZUubBPQ@mail.gmail.com/

This requires submitting a proper patch to the LKML and the Rust for Linux mailing list. Please recall to test your changes (including generating the documentation if changed, running the Rust doctests if changed, etc.), to justify the commit well in the message (""what"" & ""why""), to use a proper title for the commit, to sign your commit under the Developer's Certificate of Origin and to add a Suggested-by: tag, and a Link: tag to this issue. Please see https://docs.kernel.org/process/submitting-patches.html and https://rust-for-linux.com/contributing for details.

Please take this issue only if you are new to the kernel development process and you would like to use it as a test to submit your first patch to the kernel. Please do not take it if you do not plan to make other contributions to the kernel.