arm64: defconfig: Enable TI_SCI related configs

Enable TI System Control Interface (TI_SCI) Message Protocol library
and it's relevant power management drivers using this library.

TI's AM6 SoC uses this TI_SCI library to communicate to its system
controller(DMSC). While at it, enable TI_MESSAGE_MANAGER mailbox driver
using which this communication happens.

Signed-off-by: Lokesh Vutla <lokeshvutla@ti.com>
Acked-by: Nishanth Menon <nm@ti.com>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>