usb: phy-msm-ssusb: Add USB3 core clock

This PHY uses QSCRATCH registers which technically belong
in the USB3 controller IO space, therefore reads/writes to
them require the USB 3 master clock to be turned on. Since
the init() and set_suspend() routines could be executed while
the controller is in low power mode, explicity turn on the
clocks in order to guarantee clocked register access.

Change-Id: I4f61ab0afb70c991b29d69df93cfd49b9fb83aa8
Signed-off-by: Jack Pham <jackp@codeaurora.org>