m68k: mark PMD folded and expose number of page table levels

We would want to use number of page table level to define mm_struct.
Let's expose it as CONFIG_PGTABLE_LEVELS.

Core mm expects __PAGETABLE_{PUD,PMD}_FOLDED to be defined if these page
table levels folded.
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Tested-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

arch/m68k/Kconfig

@@ -67,6 +67,10 @@ config HZ
 	default 1000 if CLEOPATRA
 	default 100
 
+config PGTABLE_LEVELS
+	default 2 if SUN3 || COLDFIRE
+	default 3
+
 source "init/Kconfig"
 
 source "kernel/Kconfig.freezer"