sun50i: a64: teres_i: Fix broken SPL_TEXT_BASE

SPL_TEXT_BASE was moved into Kconfig, which previously part of
include/configs before this teres_i support gets merged.

Fix it by explicitly define in defconfig like other boards does.

Signed-off-by: Jonas Smedegaard <dr@jones.dk>
Signed-off-by: Jagan Teki <jagan@amarulasolutions.com>