hw/fsi: Introduce IBM's FSI master

hw/fsi: Introduce IBM's FSI master

This is a part of patchset where IBM's Flexible Service Interface is
introduced.

This commit models the FSI master. CFAM is hanging out of FSI master which is a bus controller.

The FSI master: A controller in the platform service processor (e.g.
BMC) driving CFAM engine accesses into the POWER chip. At the
hardware level FSI is a bit-based protocol supporting synchronous and
DMA-driven accesses of engines in a CFAM.

Signed-off-by: Andrew Jeffery <andrew@aj.id.au>
Signed-off-by: Ninad Palsule <ninad@linux.ibm.com>
Reviewed-by: Cédric Le Goater <clg@kaod.org>
[ clg: - move FSICFAMState object under FSIMasterState
       - introduced fsi_master_init()
       - reworked fsi_master_realize()
       - dropped FSIBus definition ]
Signed-off-by: Cédric Le Goater <clg@kaod.org>