[IA64] contig.c: fix bug in DMA-zone initialization

Below is a patch that fixes count_dma_pages().  Without this fix, only
memory areas entirely below MAX_DMA_ADDRESS are counted as DMA-pages.
While it doesn't really make a difference in practice (MAX_DMA_ADDRESS
is equal to ~0UL on zx1), it's clearly not what was intended to be
there.  I found the bug only because I briefly experimented with
lowering MAX_DMA_ADDRESS.

Tony> The discontig.c version of this code already gets this right.
Signed-off-by: David Mosberger-Tang <davidm@hpl.hp.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>

arch/ia64/mm/contig.c

@@ -214,8 +214,8 @@ count_dma_pages (u64 start, u64 end, void *arg)
 {
 	unsigned long *count = arg;
 
-	if (end <= MAX_DMA_ADDRESS)
-		*count += (end - start) >> PAGE_SHIFT;
+	if (start < MAX_DMA_ADDRESS)
+		*count += (min(end, MAX_DMA_ADDRESS) - start) >> PAGE_SHIFT;
 	return 0;
 }
 #endif