[S390] mm: add ZONE_DMA to 31-bit config again

Add ZONE_DMA to 31-bit config again. The performance gain is minimal
and hardly anybody cares anymore about a 31-bit kernel.
So add ZONE_DMA again to help with SLAB_CACHE_DMA removal for
!CONFIG_ZONE_DMA configurations.
Acked-by: David Rientjes <rientjes@google.com>
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>

arch/s390/Kconfig

@@ -2,7 +2,7 @@ config MMU
 	def_bool y
 
 config ZONE_DMA
-	def_bool y if 64BIT
+	def_bool y
 
 config LOCKDEP_SUPPORT
 	def_bool y

arch/s390/appldata/appldata_mem.c

@@ -92,9 +92,7 @@ static void appldata_get_mem_data(void *data)
 	mem_data->pswpin     = ev[PSWPIN];
 	mem_data->pswpout    = ev[PSWPOUT];
 	mem_data->pgalloc    = ev[PGALLOC_NORMAL];
-#ifdef CONFIG_ZONE_DMA
 	mem_data->pgalloc    += ev[PGALLOC_DMA];
-#endif
 	mem_data->pgfault    = ev[PGFAULT];
 	mem_data->pgmajfault = ev[PGMAJFAULT];
 

arch/s390/mm/init.c

@@ -119,9 +119,7 @@ void __init paging_init(void)
 	sparse_memory_present_with_active_regions(MAX_NUMNODES);
 	sparse_init();
 	memset(max_zone_pfns, 0, sizeof(max_zone_pfns));
-#ifdef CONFIG_ZONE_DMA
 	max_zone_pfns[ZONE_DMA] = PFN_DOWN(MAX_DMA_ADDRESS);
-#endif
 	max_zone_pfns[ZONE_NORMAL] = max_low_pfn;
 	free_area_init_nodes(max_zone_pfns);
 	fault_init();