DA850 EVM: add information regarding DA850 in README.davinci

The README.davinci in documentation folder is missing information
regarding DA850 which is a supported DaVinci device.

Add this information.

Signed-off-by: Sekhar Nori <nsekhar@ti.com>
Signed-off-by: Sandeep Paulraj <s-paulraj@ti.com>
1 file changed