IB/ipath: Fix EEPROM read when driver is compiled with -Os

The EEPROM is read via programmable I/O pins. When the driver
is compiled -Os, the CPU can speculatively read the I/O
value before it is valid.  This patch fixes the problem.

Signed-off-by: Bryan O'Sullivan <bryan.osullivan@qlogic.com>
Signed-off-by: Roland Dreier <rolandd@cisco.com>

drivers/infiniband/hw/ipath/ipath_eeprom.c

@@ -187,6 +187,7 @@ bail:
 static void i2c_wait_for_writes(struct ipath_devdata *dd)
 {
 	(void)ipath_read_kreg32(dd, dd->ipath_kregs->kr_scratch);
+	rmb();
 }
 
 static void scl_out(struct ipath_devdata *dd, u8 bit)