ppc/xive2: Introduce a XIVE2 core framework

ppc/xive2: Introduce a XIVE2 core framework

The XIVE2 interrupt controller of the POWER10 processor as the same
logic as on POWER9 but its SW interface has been largely reworked. The
interrupt controller has a new register interface, different BARs,
extra VSDs. These will be described when we add the device model for
the baremetal machine.

The XIVE internal structures for the EAS, END, NVT have different
layouts which is a problem for the current core XIVE framework. To
avoid adding too much complexity in the XIVE models, a new XIVE2 core
framework is introduced. It duplicates the models which are closely
linked to the XIVE internal structures : Xive2Router and
Xive2ENDSource and reuses the XiveSource, XivePresenter, XiveTCTX
models, as they are more generic.

Reviewed-by: Daniel Henrique Barboza <danielhb413@gmail.com>
Signed-off-by: Cédric Le Goater <clg@kaod.org>