interrupt_controller: gicv3_its: Implement Indirect Two-level table

When the ITS is configured with a large number of DeviceID bits,
up to 32, the Device Translation Table can be configured as
"indirect" mode consisting of a 2-level table with the first
level entries pointing to a second level table for each
group of DeviceIDs.

This is necessary to support platforms with DeviceID bits > 16.

Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>