powerpc/powernv/pci: Remove MVE code

With IODA1 support gone the OPAL calls to set MVE are dead code. Remove
them.

Signed-off-by: Joel Stanley <joel@jms.id.au>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://msgid.link/20230613045202.294451-3-joel@jms.id.au