configs: move CONFIG_SPL_TEXT_BASE to Kconfig

Moved CONFIG_SPL_TEXT_BASE to common/spl/Kconfig and migrate existing
values.

Signed-off-by: Simon Goldschmidt <simon.k.r.goldschmidt@gmail.com>
[trini: Re-run migration]
Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/configs/opos6uldev_defconfig b/configs/opos6uldev_defconfig
index 5397deb..6a5e8cc 100644
--- a/configs/opos6uldev_defconfig
+++ b/configs/opos6uldev_defconfig
@@ -23,6 +23,7 @@
 CONFIG_DEFAULT_FDT_FILE="imx6ul-opos6uldev.dtb"
 CONFIG_VERSION_VARIABLE=y
 CONFIG_BOUNCE_BUFFER=y
+CONFIG_SPL_TEXT_BASE=0x00908000
 CONFIG_SPL_BOARD_INIT=y
 CONFIG_SPL_ENV_SUPPORT=y
 CONFIG_SPL_WATCHDOG_SUPPORT=y