powernv/cpuidle: Fix idle states all being marked invalid

Commit 9c7b185a ("powernv/cpuidle: Parse dt idle properties into
global structure") parses dt idle states into structs, but never marks
them valid. This results in all idle states being lost.

Fixes: 9c7b185a ("powernv/cpuidle: Parse dt idle properties into global structure")
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Acked-by: Akshay Adiga <akshay.adiga@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>