arm/dts: msm9625: Enable link power management support

Link power management (a.k.a L1) is similar to the existing usb bus
suspend/resume/remote-wakeup, but has transitional latencies of tens
of microseconds between power states.

Change-Id: I0f22b1af0f3490c8740085c7c39d0b061a046c50
Signed-off-by: Shimrit Malichi <smalichi@codeaurora.org>