[ARM] Fix iop3xx macro

Macro arguments used in expressions should have parens.  This avoids
warnings such as:

drivers/serial/8250.c:1951: warning: suggest parentheses around arithmetic in operand of |
Acked-by: Dan Williams <dan.j.williams@intel.com>
Acked-by: Lennert Buytenhek <buytenh@wantstofly.org>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

include/asm-arm/hardware/iop3xx.h

@@ -231,7 +231,7 @@ extern int init_atu;
 					IOP3XX_PCI_IO_WINDOW_SIZE - 1)
 #define IOP3XX_PCI_UPPER_IO_VA		(IOP3XX_PCI_LOWER_IO_VA +\
 					IOP3XX_PCI_IO_WINDOW_SIZE - 1)
-#define IOP3XX_PCI_IO_PHYS_TO_VIRT(addr) (((u32) addr -\
+#define IOP3XX_PCI_IO_PHYS_TO_VIRT(addr) (((u32) (addr) -\
 					IOP3XX_PCI_LOWER_IO_PA) +\
 					IOP3XX_PCI_LOWER_IO_VA)