iwlwifi: pcie: Set scheduler to work on auto mode

During NIC initialization shared HW is reset and this disables the
scheduler. Some HW platforms do not activate the scheduler after it.
Consequently all HCMD sent by the driver stay at the queues which cause
to queue stuck.
Set the scheduler to work on auto active mode so it would be activated upon
change over one of the queues' write pointer.

Signed-off-by: Haim Dreyfuss <haim.dreyfuss@intel.com>
Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>