powerpc/mm: Allow ARCH_FORCE_MAX_ORDER up to 12

Christophe reported that the change to ARCH_FORCE_MAX_ORDER to limit the
range to 10 had broken his ability to configure hugepages:

  # echo 1 > /sys/kernel/mm/hugepages/hugepages-8192kB/nr_hugepages
  sh: write error: Invalid argument

Several of the powerpc defconfigs previously set the
ARCH_FORCE_MAX_ORDER value to 12, via the definition in
arch/powerpc/configs/fsl-emb-nonhw.config, used by:

  mpc85xx_defconfig
  mpc85xx_smp_defconfig
  corenet32_smp_defconfig
  corenet64_smp_defconfig
  mpc86xx_defconfig
  mpc86xx_smp_defconfig

Fix it by increasing the allowed range to 12 to restore the previous
behaviour.

Fixes: 358e526a ("powerpc/mm: Reinstate ARCH_FORCE_MAX_ORDER ranges")
Reported-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Closes: https://lore.kernel.org/all/8011d806-5b30-bf26-2bfe-a08c39d57e20@csgroup.eu/


Tested-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://msgid.link/20230824122849.942072-1-mpe@ellerman.id.au