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/P2020RDB-PC_SPIFLASH_defconfig b/configs/P2020RDB-PC_SPIFLASH_defconfig
index df72a7d..6f18acf 100644
--- a/configs/P2020RDB-PC_SPIFLASH_defconfig
+++ b/configs/P2020RDB-PC_SPIFLASH_defconfig
@@ -19,6 +19,7 @@
 CONFIG_BOARD_EARLY_INIT_F=y
 CONFIG_BOARD_EARLY_INIT_R=y
 # CONFIG_SPL_FRAMEWORK is not set
+CONFIG_SPL_TEXT_BASE=0xf8f81000
 CONFIG_SPL_ENV_SUPPORT=y
 CONFIG_SPL_I2C_SUPPORT=y
 CONFIG_SPL_MPC8XXX_INIT_DDR_SUPPORT=y