In get_ite() we currently return the caller some of the fields of an
Interrupt Table Entry via a set of pointer arguments, and validate
some of them internally (interrupt type and valid bit) to return a
simple true/false 'valid' indication. Define a new ITEntry struct
which has all the fields that the in-memory ITE has, and bring the
get_ite() function in to line with get_dte() and get_cte().

This paves the way for handling virtual interrupts, which will want
a different subset of the fields in the ITE. Handling them under
the old "lots of pointer arguments" scheme would have meant a
confusingly large set of arguments for this function.

The new struct ITEntry is obviously confusably similar to the
existing IteEntry struct, whose fields are the raw 12 bytes
of the in-memory ITE. In the next commit we will make update_ite()
use ITEntry instead of IteEntry, which will allow us to delete
the IteEntry struct and remove the confusion.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20220201193207.2771604-9-peter.maydell@linaro.org