m32r: mm: fix build warning

While building we are getting warnings:

  arch/m32r/mm/init.c:63:17: warning: unused variable 'low'
  arch/m32r/mm/init.c:62:17: warning: unused variable 'max_dma'

max_dma and low are only used if CONFIG_MMU is defined.  Lets declare
the variables inside the #ifdef.
Signed-off-by: Sudip Mukherjee <sudip@vectorindia.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

arch/m32r/mm/init.c

@@ -59,21 +59,24 @@ void free_initrd_mem(unsigned long, unsigned long);
 void __init zone_sizes_init(void)
 {
 	unsigned long  zones_size[MAX_NR_ZONES] = {0, };
-	unsigned long  max_dma;
-	unsigned long  low;
 	unsigned long  start_pfn;
 
 #ifdef CONFIG_MMU
-	start_pfn = START_PFN(0);
-	max_dma = virt_to_phys((char *)MAX_DMA_ADDRESS) >> PAGE_SHIFT;
-	low = MAX_LOW_PFN(0);
-
-	if (low < max_dma){
-		zones_size[ZONE_DMA] = low - start_pfn;
-		zones_size[ZONE_NORMAL] = 0;
-	} else {
-		zones_size[ZONE_DMA] = low - start_pfn;
-		zones_size[ZONE_NORMAL] = low - max_dma;
+	{
+		unsigned long  low;
+		unsigned long  max_dma;
+
+		start_pfn = START_PFN(0);
+		max_dma = virt_to_phys((char *)MAX_DMA_ADDRESS) >> PAGE_SHIFT;
+		low = MAX_LOW_PFN(0);
+
+		if (low < max_dma) {
+			zones_size[ZONE_DMA] = low - start_pfn;
+			zones_size[ZONE_NORMAL] = 0;
+		} else {
+			zones_size[ZONE_DMA] = low - start_pfn;
+			zones_size[ZONE_NORMAL] = low - max_dma;
+		}
 	}
 #else
 	zones_size[ZONE_DMA] = 0 >> PAGE_SHIFT;