[S390] Cleanup page table definitions.

- De-confuse the defines for the address-space-control-elements
  and the segment/region table entries.
- Create out of line functions for page table allocation / freeing.
- Simplify get_shadow_xxx functions.

Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
diff --git a/arch/s390/mm/Makefile b/arch/s390/mm/Makefile
index f95449b..6640193 100644
--- a/arch/s390/mm/Makefile
+++ b/arch/s390/mm/Makefile
@@ -2,6 +2,6 @@
 # Makefile for the linux s390-specific parts of the memory manager.
 #
 
-obj-y	 := init.o fault.o extmem.o mmap.o vmem.o
+obj-y	 := init.o fault.o extmem.o mmap.o vmem.o pgtable.o
 obj-$(CONFIG_CMM) += cmm.o