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/wb50n_defconfig b/configs/wb50n_defconfig
index b6e22f5..71a95b3 100644
--- a/configs/wb50n_defconfig
+++ b/configs/wb50n_defconfig
@@ -11,6 +11,7 @@
 CONFIG_FIT=y
 CONFIG_SYS_EXTRA_OPTIONS="SAMA5D3,SYS_USE_NANDFLASH"
 CONFIG_BOOTDELAY=3
+CONFIG_SPL_TEXT_BASE=0x300000
 CONFIG_SPL_NAND_SUPPORT=y
 CONFIG_HUSH_PARSER=y
 CONFIG_CMD_BOOTZ=y