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/stm32f746-disco_defconfig b/configs/stm32f746-disco_defconfig
index 32a528f..5fa892f 100644
--- a/configs/stm32f746-disco_defconfig
+++ b/configs/stm32f746-disco_defconfig
@@ -13,6 +13,7 @@
 # CONFIG_DISPLAY_CPUINFO is not set
 # CONFIG_DISPLAY_BOARDINFO is not set
 CONFIG_BOARD_EARLY_INIT_F=y
+CONFIG_SPL_TEXT_BASE=0x8000000
 CONFIG_SYS_PROMPT="U-Boot > "
 CONFIG_AUTOBOOT_KEYED=y
 CONFIG_AUTOBOOT_PROMPT="Hit SPACE in %d seconds to stop autoboot.\n"