iwlwifi: remove PA type configuration

No need to have a special config variable
for the PA type, we can just use the
additional NIC config function to config
the hardware correctly.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Wey-Yi Guy <wey-yi.w.guy@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>