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

@@ -59,22 +59,25 @@ 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
+	{
+		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){
+		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;
 	zones_size[ZONE_NORMAL] = __MEMORY_SIZE >> PAGE_SHIFT;