iwlwifi: split POWER_PMI status bit

Move the POWER_PMI to the op_mode where it is changed.  The trans needs
to check it frequently, so shadow the status in the trans and update it
in trans when it infrequently changes.

Signed-off-by: Don Fry <donald.h.fry@intel.com>
Signed-off-by: Wey-Yi Guy <wey-yi.w.guy@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>