sun50i: h6: Fix Beelink GS1 board config

SPL_TEXT_BASE has been moved to Kconfig with commit:
f89d6133 configs: move CONFIG_SPL_TEXT_BASE to Kconfig

But Beelink GS1 config file has been introduced in the
same time without this modification.

Fix this by settings the CONFIG_SPL_TEXT_BASE

Suggested-by: Jonas Smedegaard <dr@jones.dk>
Signed-off-by: Clément Péron <peron.clem@gmail.com>
Reviewed-by: Jagan Teki <jagan@amarulasolutions.com>