the `bind_interrupts` macro creates a `struct` for the interrupts. it
was so far not possible to document those (except for STM32) and there
was no generic documentation being generated/added either, thus the
`missing_docs` lint was triggered for consumers which enabled it.
with this change it is now possible to manually add a comment on the
`struct` being defined in the macro invocation.
to show that this works one RP example has been modified accordingly.
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