ppc/pnv: make PECs create and realize PHB4s

ppc/pnv: make PECs create and realize PHB4s

This patch changes the design of the PEC device to create and realize PHB4s
instead of PecStacks. After all the recent changes, PHB4s now contain all
the information needed for their proper functioning, not relying on PecStack
in any capacity.

All changes are being made in a single patch to avoid renaming parts of
the PecState and leaving the code in a strange way. E.g. rename
PecClass->num_stacks to num_phbs, which would then read a
pnv_pec_num_stacks[] array. To avoid mixing the old and new design more
than necessary it's clearer to do these changes in a single step.

The name changes made are:

- in PnvPhb4PecState:
  * rename 'num_stacks' to 'num_phbs'
  * remove the pec->stacks[] array. Current code relies on the
pec->stacks[] obj acting as a simple container, without ever accessing
pec->stacks[] for any other purpose. Instead of converting this into a
pec->phbs[] array, remove it

- in PnvPhb4PecClass, rename *num_stacks to *num_phbs;

- pnv_pec_num_stacks[] is renamed to pnv_pec_num_phbs[].

The logical changes:

- pnv_pec_default_phb_realize():
  * init and set the properties of the PnvPHB4 qdev
  * do not use stack->phb anymore;

- pnv_pec_realize():
  * use the new default_phb_realize() to init/realize each PHB if
running with defaults;

- pnv_pec_instance_init(): removed since we're creating the PHBs during
pec_realize();

- pnv_phb4_get_stack():
  * renamed to pnv_phb4_get_pec() and returns a PnvPhb4PecState*;

- pnv_phb4_realize(): use 'phb->pec' instead of 'stack'.

This design change shouldn't caused any behavioral change in the runtime
of the machine.

Signed-off-by: Daniel Henrique Barboza <danielhb413@gmail.com>
Reviewed-by: Cédric Le Goater <clg@kaod.org>
Message-Id: <20220114180719.52117-7-danielhb413@gmail.com>
Signed-off-by: Cédric Le Goater <clg@kaod.org>