Bluetooth: hci_qca: use the power sequencer for wcn6750

Older boards are having entry "enable-gpios" in dts, we can safely assume
latest boards which are supporting PMU node enrty will support power
sequencer.

Signed-off-by: Janaki Ramaiah Thota <quic_janathot@quicinc.com>
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>