board: ti: j7200: Introduce support for j7200 build targets

j7200-evm has minor differences with j721e-evm based on the IPs
available in the SoC. Introduce separate build targets for j7200-evm
to incorporate the differences.

Signed-off-by: Lokesh Vutla <lokeshvutla@ti.com>
Reviewed-by: Suman Anna <s-anna@ti.com>