arm/dt: msm9625: Add MSM USB BAM support

Add device tree entries for the MSM USB BAM. Add AUXDATA
to create "usb_bam" sysfs node for existing userspace scripts.

Also clarify device tree documentation on the use of reg-names
and interrupt-names properties of the USB BAM node.

Change-Id: I5a53d1f9c0416af58ea9c36d3618f4d328f9cf44
Signed-off-by: Jack Pham <jackp@codeaurora.org>