ichspi.c: make REGWRITE* macros safer

'+' does have a quite high precedence so "calling" those macros with a
term including weaker operators in the off parameter may have unexpected
consequences.

Corresponding to flashrom svn r1359.

Signed-off-by: Stefan Tauner <stefan.tauner@alumni.tuwien.ac.at>
Acked-by: Carl-Daniel Hailfinger <c-d.hailfinger.devel.2006@gmx.net>
diff --git a/ichspi.c b/ichspi.c
index b4eb236..a78034a 100644
--- a/ichspi.c
+++ b/ichspi.c
@@ -216,9 +216,9 @@
 	return mmio_readb(ich_spibar + X);
 }
 
-#define REGWRITE32(off,val) mmio_writel(val, ich_spibar+off)
-#define REGWRITE16(off,val) mmio_writew(val, ich_spibar+off)
-#define REGWRITE8(off,val)  mmio_writeb(val, ich_spibar+off)
+#define REGWRITE32(off, val) mmio_writel(val, ich_spibar+(off))
+#define REGWRITE16(off, val) mmio_writew(val, ich_spibar+(off))
+#define REGWRITE8(off, val)  mmio_writeb(val, ich_spibar+(off))
 
 /* Common SPI functions */
 static int find_opcode(OPCODES *op, uint8_t opcode);