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/rock2_defconfig b/configs/rock2_defconfig
index 2ea9de2..7639b55 100644
--- a/configs/rock2_defconfig
+++ b/configs/rock2_defconfig
@@ -15,6 +15,7 @@
 CONFIG_DEFAULT_FDT_FILE="rk3288-rock2-square.dtb"
 # CONFIG_DISPLAY_CPUINFO is not set
 CONFIG_DISPLAY_BOARDINFO_LATE=y
+CONFIG_SPL_TEXT_BASE=0xff704000
 CONFIG_SPL_STACK_R=y
 CONFIG_SPL_STACK_R_MALLOC_SIMPLE_LEN=0x2000
 CONFIG_CMD_GPIO=y