board: ti: j784s4: Add board support for J784S4 EVM

Add board files for J784S4 EVM.

SYS_DISABLE_DCACHE_OPS is selected in the Kconfig because
J784S4/AM69 are a coherent architecture at A72 level by
MSMC support.

Signed-off-by: Hari Nagalla <hnagalla@ti.com>
Signed-off-by: Dasnavis Sabiya <sabiya.d@ti.com>
Signed-off-by: Apurva Nandan <a-nandan@ti.com>
Reviewed-by: Tom Rini <trini@konsulko.com>
Reviewed-by: Tom Rini <trini@konsulko.com>
Tested-by: Marcel Ziswiler <marcel.ziswiler@toradex.com> # AM69-SK