iwl3945: move iwl_power_initialize()

iwl_power_initialize() initializes driver data (not device hardware), and does
not need to execute more than once (when the driver initializes).  Therefore, it
does not belong in iwl3945_apm_init(), which initializes hardware, and may run
more than once.

Move it to iwl3945_pci_probe(), where it will run only once.  This agrees
with similar placement in iwl-agn.c's iwl_pci_probe(), although placement
under "services" seemed more appropriate than under "mac80211".

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