usb: qmp: phy: Fix handling of ref_clk and ref_clk_src

Current code is keeping ref_clk and ref_clk_src always ON although
USB cable is not connected. Keeping ref_clk as ON results into leakage
current whereas keeping ref_clk_src as ON results into more power
consumption with XOSD case.

Change-Id: Ibe72139065144b5caa1935b79473c451b948f38a
Signed-off-by: Mayank Rana <mrana@codeaurora.org>