usb: dwc3-msm: Add vote for BUS scaling on cable connect

To support high throughputs over USB3, add appropriate
BUS scaling votes in the driver. Also, use API provided
by bus driver to parse device tree node for vectors
instead of passing the bandwidth vectors using boards file.

Change-Id: Icb98e0a1ecd298c8d350ef7a53f47c1b20849c2d
Signed-off-by: Manu Gautam <mgautam@codeaurora.org>