x86, iomap: Fix wrong page aligned size calculation in ioremapping code

x86 early_iounmap(): fix off-by-one error in page alignment of allocation
size for sizes where size%PAGE_SIZE==1.
Signed-off-by: NFlorian Zumbiehl <florz@florz.de>
LKML-Reference: <201007202219.o6KMJlES021058@imap1.linux-foundation.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NH. Peter Anvin <hpa@linux.intel.com>

arch/x86/mm/ioremap.c

@@ -611,7 +611,7 @@ void __init early_iounmap(void __iomem *addr, unsigned long size)
 		return;
 	}
 	offset = virt_addr & ~PAGE_MASK;
-	nrpages = PAGE_ALIGN(offset + size - 1) >> PAGE_SHIFT;
+	nrpages = PAGE_ALIGN(offset + size) >> PAGE_SHIFT;
 
 	idx = FIX_BTMAP_BEGIN - NR_FIX_BTMAPS*slot;
 	while (nrpages > 0) {