SBUS support for BeagleBone Blue

[Ddevendra]

This is recreation of Taranis sbus support.
In this PR I have just included the SBUS driver with a couple of other very minor fixes.

What changes does this PR contains:

• isolated SBUS driver for easy review and merging
• Taranis sbus support had merge conflicts with upstream, resolves those conflicts

Further Suggestions:

• separate PR for "custom configurable baudrate for UART"
• proper documentation on testing/running SBUS receiver with BeagleBone Blue
• SBUS support for BBB and BBAI

[Ddevendra]

@StrawsonDesign
@jadonk
@lorforlinux
I am new contributor to BeagleBoard.org, can you please review this and suggest what else could be done on beginner's level.

[jadonk]

Thanks! Please don't hesitate to bug me again if a few days if I haven't reviewed and/or merged.