ARM: dts: msm: Add secondary USB host for MSM8994

The MSM8994 contains a secondary instance of a USB host
controller paired with the new QUSB2 PHY. Add device tree
nodes to describe them.

Leave these disabled in the base msm8994.dtsi and enable
them only on CDP, as VBUS power is required. Also add
the VBUS regulator device which is controled by GPIO 5
on the PMI8994.

Change-Id: I7bb69f6b7066c9fe3fd56200dea3f34fbe44d38b
Signed-off-by: Jack Pham <jackp@codeaurora.org>