qtnfmac: improve control path timeout handling

Control path will not be operational after firmware failure. Change bus
state to QTNF_FW_STATE_EP_DEAD after the control path timeout.
Don't wait for timeout if control path is already dead.

Signed-off-by: Dmitry Lebed <dlebed@quantenna.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>