phy: add SPDX identifier to QMP and QUSB2 PHY drivers

The SPDX identifier is a legally binding shorthand, which
can be used instead of the full boiler plate text.

Signed-off-by: Manu Gautam <mgautam@codeaurora.org>
Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>