powerpc/64s: Power9 has no LPCR[VRMASD] field so don't set it

Power9/ISAv3 has no VRMASD field in LPCR, we shouldn't be setting reserved bits,
so don't set them on Power9.

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>