ARM: dts: msm: Add support for UART dtsi on sdxprairie

Initial support for all BLSP UART instances with default
configuration and disabled state such that clients can overwrite
and enable respective instance as per need.

Change-Id: Ie28c060d368c9f4c8d1bc4489a9a348ba46d9ca0
Signed-off-by: Mukesh Kumar Savaliya <msavaliy@codeaurora.org>