powerpc: Add POWER9 architected mode to cputable

PVR value of 0x0F000005 means we are arch v3.00 compliant (i.e. POWER9).

Acked-by: Michael Neuling <mikey@neuling.org>
Signed-off-by: Russell Currey <ruscur@russell.cc>
[mpe: Don't set num_pmcs, so we keep the PMU fields from the raw entry]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>