ARM: dts: msm: Move usb_otg from dtsi to dts file for msm8939 skuk

usb_otg is using smb1360_otg_supply which is defined in
dts file. To be consistent, move usb_otg to same dts
file.

Change-Id: I0b83e9846a05fe35953f3cdc76c19b88b743194f
Signed-off-by: Maria Yu <aiquny@codeaurora.org>