USB: dwc3-msm: Turn on iface_clk before accessing AHB2PHY registers

On some platforms, USB3 controller sits on PCNOC instead of SNOC.
In this case, it is required to turn on iface_clk(pcnoc_axi_clk)
and cfg_ahb_clk before accessing AHB2PHY register. Hence make
required change for turning on iface_clk before AHB2PHY register
access.

Change-Id: Idf069a07edfb3e03e62cefa91fbeaa4f297af89a
Signed-off-by: Vijayavardhan Vennapusa <vvreddy@codeaurora.org>