iwlwifi: make iwl-power.c more readable

This patch rearrange code in iwl-power.c function to make it a little more
readable. No functional changes.

Signed-off-by: Tomas Winkler <tomas.winkler@intel.com>
Signed-off-by: Reinette Chatre <reinette.chatre@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>