powerpc/powernv/npu: Check mmio_atsd array bounds when populating

powerpc/powernv/npu: Check mmio_atsd array bounds when populating

BugLink: https://bugs.launchpad.net/bugs/1819989
A broken device tree might contain more than 8 values and introduce hard
to debug memory corruption bug. This adds the boundary check.

Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
(cherry picked from commit 135ef954051b102870a8d47a8eb822af1f1b1ec1)
Signed-off-by: Jose Ricardo Ziviani <joserz@linux.ibm.com>
Acked-by: Kamal Mostafa <kamal@canonical.com>
Acked-by: Kleber Souza <kleber.souza@canonical.com>
Signed-off-by: Khalid Elmously <khalid.elmously@canonical.com>