add the documenatation
Signed-off-by: NWayne Ren <wei.ren@synopsys.com>

* the initial support of synopsys designware arc processor
* the initial support of synospsy ARC EM Starter Kit
* the bsp code is based on embarc which is a common SDK for
all synopsys ARC-based boards
* use "scons --gdb" to debug emsk with em9d configuration
* for detailed board information, pls go embarc.org
Signed-off-by: NWayne Ren <wei.ren@synopsys.com>