powerpc: Enforce sane MAX_ORDER

powerpc uses CONFIG_FORCE_MAX_ZONEORDER, and some things depend on it
being at least 10 when 64k pages are not configured (notably the dart
iommu code with CONFIG_PM). The defaults are fine, but when going from a
64K pages config to one without 64K pages, MAX_ORDER stays at 9 which is
too low for 4K pages.

This patch makes the Kconfig enforce at least the defaults.
Signed-off-by: Johannes Berg <johannes@sipsolutions.net>
Acked-by: Timur Tabi <timur@freescale.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

arch/powerpc/Kconfig

@@ -415,8 +415,11 @@ config PPC_64K_PAGES
 
 config FORCE_MAX_ZONEORDER
 	int "Maximum zone order"
+	range 9 64 if PPC_64K_PAGES
 	default "9" if PPC_64K_PAGES
+	range 13 64 if PPC64 && !PPC_64K_PAGES
 	default "13" if PPC64 && !PPC_64K_PAGES
+	range 11 64
 	default "11"
 	help
 	  The kernel memory allocator divides physically contiguous memory