Everything is in place to switch to per-ITS translation caches. Start
using the per-ITS cache to avoid the lock serialization related to the
global translation cache. Explicitly check for out-of-range device and
event IDs as the cache index is packed based on the range the ITS
actually supports.

Take the RCU read lock to protect against the returned descriptor being
freed while trying to take a reference on it, as it is no longer
necessary to acquire the lpi_list_lock.
Signed-off-by: Oliver Upton <oliver.upton@linux.dev>
Link: https://lore.kernel.org/r/20240422200158.2606761-11-oliver.upton@linux.devSigned-off-by: Marc Zyngier <maz@kernel.org>