pseries: Remove unused callbacks from sPAPR VIO bus state

pseries: Remove unused callbacks from sPAPR VIO bus state

The original QOMification of the spapr VIO devices in 3954d33 "spapr:
convert to QEMU Object Model (v2)" moved some callbacks from the
VIOsPAPRBus structure to the VIOsPAPRDeviceClass.  Except, that it
forgot to actually remove them from the VIOsPAPRBus structure (which
still exists, though it doesn't fulfill quite the same function as it
did pre-QOM).

This patch removes those now unused callback fields.

Signed-off-by: David Gibson <[email protected]>
Reviewed-by: Alexey Kardashevskiy <[email protected]>
Reviewed-by: Thomas Huth <[email protected]>