iwlwifi: fix otp access init

Polling function returns positive time if polling was needed to
read value. This is still success.

Signed-off-by: Reinette Chatre <reinette.chatre@intel.com>
CC: Wey-Yi Guy <wey-yi.w.guy@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>