iwlwifi: replace iwl_poll_direct_bit with iwl_poll_bit for CSR access

Replace iwl_poll_direct_bit with iwl_poll_bit when accessing CSR registers.
There is no need to power up the mac to access CSR registers.

Signed-off-by: Abhijeet Kolekar <abhijeet.kolekar@intel.com>
Acked-by: Ben M Cahill <ben.m.cahill@intel.com>
Signed-off-by: Reinette Chatre <reinette.chatre@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>