powerpc/64s: Add all POWER9 features to CPU_FTRS_ALWAYS

It's not a bug to have features missing in CPU_FTR_ALWAYS, but it is a
missed opportunity for optimisation.

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