configs: am65x_evm_r5: Add initial support

Add initial defconfig support for AM65x
that runs on R5.

Reviewed-by: Tom Rini <trini@konsulko.com>
Signed-off-by: Lokesh Vutla <lokeshvutla@ti.com>
Signed-off-by: Andreas Dannenberg <dannenberg@ti.com>
Signed-off-by: Keerthy <j-keerthy@ti.com>