This commit adds basic Cavium ThunderX 88xx board definitions and support.

Signed-off-by: Sergey Temerkhanov <s.temerkhanov@gmail.com>
Signed-off-by: Radha Mohan Chintakuntla <rchintakuntla@cavium.com>
[trini: Drop CONFIG_SYS_GENERIC_BOARD define]
Signed-off-by: Tom Rini <trini@konsulko.com>