powerpc/powernv/pci: Drop VF MPS fixup

The MPS field in the VF config space is marked as reserved in current
versions of the SR-IOV spec. In other words, this fixup doesn't do
anything.

Signed-off-by: Oliver O'Halloran <oohall@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20200902035159.1762596-1-oohall@gmail.com