iwlwifi: enable shadow registers for 7000

This will reduce CPU utilization. Instead of waking up the
NIC for each Tx manually, the CPU can write to a register
that will wake up the NIC automatically.

Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

diff --cc drivers/net/wireless/iwlwifi/iwl-7000.c
Simple merge