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/platinum_picon_defconfig b/configs/platinum_picon_defconfig
index 45ce2ef..786f6a4 100644
--- a/configs/platinum_picon_defconfig
+++ b/configs/platinum_picon_defconfig
@@ -16,6 +16,7 @@
 CONFIG_MISC_INIT_R=y
 CONFIG_BOUNCE_BUFFER=y
 CONFIG_BOARD_EARLY_INIT_F=y
+CONFIG_SPL_TEXT_BASE=0x00908000
 CONFIG_SPL_DMA_SUPPORT=y
 CONFIG_SPL_FS_EXT4=y
 CONFIG_SPL_I2C_SUPPORT=y