hw/ssi/pnv_spi: Make bus names distinct for each controllers of a socket

hw/ssi/pnv_spi: Make bus names distinct for each controllers of a socket

Create a spi buses with distinct names on each socket so that responders
are attached to correct SPI controllers.

Change the bus name to chipX.spi.<busnum> where X = 0..<num_sockets>

QOM tree on a 2 socket machine:
(qemu) info qom-tree
/machine (powernv10-machine)
  /chip[0] (power10_v2.0-pnv-chip)
    /pib_spic[0] (pnv-spi)
      /chip0.spi.0 (SSI)
      /xscom-spi[0] (memory-region)
  /chip[1] (power10_v2.0-pnv-chip)
    /pib_spic[0] (pnv-spi)
      /chip1.spi.0 (SSI)
      /xscom-spi[0] (memory-region)

Signed-off-by: Chalapathi V <chalapathi.v@linux.ibm.com>
Message-ID: <20250303141328.23991-4-chalapathi.v@linux.ibm.com>
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>