Convert CONFIG_USE_BOOTCOMMAND et al to Kconfig

This converts the following to Kconfig:
   CONFIG_USE_BOOTCOMMAND
   CONFIG_BOOTCOMMAND
   CONFIG_RAMBOOTCOMMAND
   CONFIG_NFSBOOTCOMMAND

Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/configs/tools-only_defconfig b/configs/tools-only_defconfig
index f482c9a..400b050 100644
--- a/configs/tools-only_defconfig
+++ b/configs/tools-only_defconfig
@@ -6,6 +6,8 @@
 CONFIG_ANDROID_BOOT_IMAGE=y
 CONFIG_FIT=y
 CONFIG_FIT_SIGNATURE=y
+CONFIG_USE_BOOTCOMMAND=y
+CONFIG_BOOTCOMMAND="run distro_bootcmd"
 CONFIG_MISC_INIT_F=y
 # CONFIG_CMD_BOOTD is not set
 # CONFIG_CMD_BOOTM is not set