A hardware bug had been discovered on 7260 / 3160 and 7265
and the workaround for this bug is to force the NIC to stay
awake as long as we have host commands in flight. This
workaround has been introduced for all NICs in a previous
patch:

b9439491 ("iwlwifi: pcie: keep the NIC awake when commands are in flight")

In newer NICs, this bug is solved, so we can let the NIC go
to sleep even when we send commands. The hardware will wake
up when we increment the scheduler write pointer.
Make the workaround conditional to only use it on affected
hardware.
Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>