usb: dwc3-msm: Explicitly set clock rates

There's no guarantee from the clock driver that the clocks used
by the DWC3 core will have the frequencies set correctly. Hence,
explicitly call clk_set_rate() at probe time to the right values.

Change-Id: I919117447b54ea004b7b7399568fd86551646eda
Signed-off-by: Jack Pham <jackp@codeaurora.org>