iwlwifi: add very first D0i3 support

When the bus is in D0i3, we can't send regular commands to
the firmware. This means that we need to add a state to
remember what is our d0i3 state and make sure that only
d0i3 exit commands can be sent.
Add flags to CMD_ flags and transport status for this
purpose.

Commands with CMD_HIGH_PRIO set are queued at the head of
the command queue, behind other high priority commands.

Commands with CMD_SEND_IN_IDLE set can be sent while the
transport is idle (without taking rpm reference).

Commands with CMD_MAKE_TRANS_IDLE set indicate that command
completion should mark the transport as idle (and release
the bus).

Commands with CMD_WAKE_UP_TRANS set instruct the transport
to exit from idle when this command is completed.

The transport is marked as idle (STATUS_TRANS_IDLE) when
the FW enters D0i3 state. This bit is cleared when it
enters D0 state again.

Process only commands with CMD_SEND_IN_IDLE flag while the
transport is idle. Other enqueued commands will be
processed only later, right after exiting D0i3.

Signed-off-by: Arik Nemtsov <arik@wizery.com>
Signed-off-by: Eliad Peller <eliadx.peller@intel.com>
Reviewed-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>