iwlagn: open/close envlope to force move BT state machine

In uCode, BT state machine need to receive open envlope
command before perform calibration; followed by close envlope
command to move to next stage.

Since Linux has two separated uCode, one for init and the second
one for runtime; we use open envlope commands for init uCode to
indicate we are ready to perform calibration operation.
But for runtime uCode, we are not doing any init calibration,
so we issue open/close envlope commands to force uCode move to
"BT COEX ON" state.

Signed-off-by: Wey-Yi Guy <wey-yi.w.guy@intel.com>