hw/intc/arm_gicv3_its: Handle virtual interrupts in process_its_cmd()

hw/intc/arm_gicv3_its: Handle virtual interrupts in process_its_cmd()

For GICv4, interrupt table entries read by process_its_cmd() may
indicate virtual LPIs which are to be directly injected into a VM.
Implement the ITS side of the code for handling this.  This is
similar to the existing handling of physical LPIs, but instead of
looking up a collection ID in a collection table, we look up a vPEID
in a vPE table.  As with the physical LPIs, we leave the rest of the
work to code in the redistributor device.

The redistributor half will be implemented in a later commit;
for now we just provide a stub function which does nothing.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20220408141550.1271295-15-peter.maydell@linaro.org