preboot: Introduce CONFIG_USE_PREBOOT and migrate CONFIG_PREBOOT
This is the same migration path as commit b6251db8c3f0 ("Kconfig:
Introduce USE_BOOTCOMMAND and migrate BOOTCOMMAND").
I also moved the description in README to the Kconfig help.
I ripped off the sentence about 'LWMON' since it is gone already.
I only let my boards migrate, leaving the rest to platform maintainers.
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
diff --git a/configs/uniphier_v7_defconfig b/configs/uniphier_v7_defconfig
index f7abf05..bb9ce1a 100644
--- a/configs/uniphier_v7_defconfig
+++ b/configs/uniphier_v7_defconfig
@@ -9,6 +9,8 @@
CONFIG_NR_DRAM_BANKS=3
# CONFIG_ARCH_FIXUP_FDT_MEMORY is not set
CONFIG_BOOTCOMMAND="run ${bootdev}script; run ${bootdev}boot"
+CONFIG_USE_PREBOOT=y
+CONFIG_PREBOOT="env exist ${bootdev}preboot && run ${bootdev}preboot"
CONFIG_LOGLEVEL=6
CONFIG_SPL_NAND_SUPPORT=y
CONFIG_SPL_NOR_SUPPORT=y