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>