iwlwifi: use iwl_poll_direct_bit in EEPROM reading

The patch replaces the current reading EEPROM loop iterations with
iwl_poll_direct_bit(). It also fixes some comment error.

Signed-off-by: Zhu Yi <yi.zhu@intel.com>
Signed-off-by: Reinette Chatre <reinette.chatre@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>