doc: fix typo in botching up ioctls

The type contained a typo `uintprt` -> `uintptr`

Signed-off-by: Federico Vaga <federico.vaga@vaga.pv.it>
Acked-by: Randy Dunlap <rdunlap@infradead.org>
Link: https://lore.kernel.org/r/20221230172328.58612-1-federico.vaga@vaga.pv.it


Signed-off-by: Jonathan Corbet <corbet@lwn.net>