usb: phy-msm-qmp: Optional reset clocks

The phy_com_reset clock and pipe_clk's reset method are
only available on certain targets. Make them optional and
don't fail if unavailable.

Change-Id: Ic97cf2f92641dc7d2dd5912fb8a7df71c9f88298
Signed-off-by: Jack Pham <jackp@codeaurora.org>