doc:it_IT: add RISC-V maintenance guidelines

Add translation for the RISC-V maintenance guidelines as part
of the translation of things related to "process/"

Signed-off-by: Federico Vaga <federico.vaga@vaga.pv.it>
Link: https://lore.kernel.org/r/20200405210647.24991-1-federico.vaga@vaga.pv.it
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
