hw/fsi: Introduce IBM's cfam

hw/fsi: Introduce IBM's cfam

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

The Common FRU Access Macro (CFAM), an address space containing
various "engines" that drive accesses on busses internal and external
to the POWER chip. Examples include the SBEFIFO and I2C masters. The
engines hang off of an internal Local Bus (LBUS) which is described
by the CFAM configuration block.

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: - moved object FSIScratchPad under FSICFAMState
       - moved FSIScratchPad code under cfam.c
       - introduced fsi_cfam_instance_init()
       - reworked fsi_cfam_realize() ]
Signed-off-by: Cédric Le Goater <clg@kaod.org>