synquacer: Add platform makefile and documentation

Add Makefile and plaform definations file.
My thanks to Daniel Thompson and Ard Biesheuvel for the bits and pieces
I've taken from their earlier work regarding build and deploy steps for
Developerbox based on Synquacer SoCs. They deserve much of the credit
for this work although, since I assembled and tested things, any blame
is probably mine.

Signed-off-by: Sumit Garg <sumit.garg@linaro.org>
Tested-by: Daniel Thompson <daniel.thompson@linaro.org>
Tested-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>