ARM: dts: msm: Include USB definitions in SDM845 SoC

Include sdm845-usb.dtsi as part of sdm845.dtsi as it applies
to all targets using this SoC.

Change-Id: I027535f25079550b6e4fb02a1724c8e1c91f0585
Signed-off-by: Jack Pham <jackp@codeaurora.org>