arm: mach-k3: Add config option for setting OP-TEE address

Much like we have for ATF, OP-TEE has a standard address that we load
it too and run it from. Add a Kconfig item for this to remove some
hard-coding and allow this address to be more easily changed.

Signed-off-by: Andrew Davis <afd@ti.com>
Acked-by: Bryan Brattlof <bb@ti.com>
Reviewed-by: Neha Malcom Francis <n-francis@ti.com>