dt-bindings: net: bluetooth: Add device tree bindings for QTI chip wcn3990

This patch enables regulators for the Qualcomm Bluetooth wcn3990
controller.

Signed-off-by: Balakrishna Godavarthi <bgodavar@codeaurora.org>
Reviewed-by: Rob Herring <robh@kernel.org>
Reviewed-by: Stephen Boyd <swboyd@chromium.org>
Reviewed-by: Matthias Kaehlcke <mka@chromium.org>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>