iwlwifi: handle the case when set power fail

Modify the power update function, when driver fail to set the power, it
should not continue move forward and try to change the rx chain
configuration.

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