phy: qcom-qusb2: Add support for runtime PM

Disable clocks and enable DP/DM wakeup interrupts when
suspending PHY.
Core driver should notify speed to PHY driver to enable
appropriate DP/DM wakeup interrupts polarity in suspend state.

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