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/alt_defconfig b/configs/alt_defconfig
index e50510a..a51c0d6 100644
--- a/configs/alt_defconfig
+++ b/configs/alt_defconfig
@@ -19,6 +19,7 @@
 CONFIG_FIT=y
 CONFIG_BOOTDELAY=3
 CONFIG_VERSION_VARIABLE=y
+CONFIG_SPL_TEXT_BASE=0xe6300000
 CONFIG_SPL_BOARD_INIT=y
 CONFIG_SPL_SYS_MALLOC_SIMPLE=y
 CONFIG_SPL_RAM_SUPPORT=y