usb: qmp: phy: Read phy reg offsets from device tree file

Reading phy register offsets from device tree prevents hard
coding of different register offset values for different
phy revisions in driver file. Add a device tree property
qcom,qmp-phy-reg-offset to store phy register offsets in
an order defined in the driver.

Change-Id: Iba97e6e8bf3bfab1372a8f7d92d5b2abdff0573e
Signed-off-by: Hemant Kumar <hemantk@codeaurora.org>