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/avnet_ultra96_rev1_defconfig b/configs/avnet_ultra96_rev1_defconfig
index 15a6827..fc4429b 100644
--- a/configs/avnet_ultra96_rev1_defconfig
+++ b/configs/avnet_ultra96_rev1_defconfig
@@ -13,6 +13,7 @@
 CONFIG_FIT_VERBOSE=y
 CONFIG_SPL_LOAD_FIT=y
 # CONFIG_DISPLAY_CPUINFO is not set
+CONFIG_SPL_TEXT_BASE=0xfffc0000
 CONFIG_SPL_OS_BOOT=y
 CONFIG_SPL_RAM_SUPPORT=y
 CONFIG_SPL_RAM_DEVICE=y