BugLink: https://bugs.launchpad.net/bugs/1892822

commit 89c140bb upstream.

Booting with a 4GB LMB size causes us to panic:

  qemu-system-ppc64: OS terminated: OS panic:
      Memory block size not suitable: 0x0

Fix pseries_memory_block_size() to handle 64 bit LMBs.

Cc: stable@vger.kernel.org
Signed-off-by: Anton Blanchard <anton@ozlabs.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20200715000820.1255764-1-anton@ozlabs.orgSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Khalid Elmously <khalid.elmously@canonical.com>
Signed-off-by: Ian May <ian.may@canonical.com>
Signed-off-by: Kelsey Skunberg <kelsey.skunberg@canonical.com>