msm: clock-krypton: Allow set rate on the usb30_master_clk cbcr

Although the parent rcg has two children, allow set_rate calls
to go through to the parent to simplify clock control.

Change-Id: Ida81014dd1339322ba6c939d1da60ecb5193f325
Signed-off-by: Patrick Daly <pdaly@codeaurora.org>