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/colibri_vf_defconfig b/configs/colibri_vf_defconfig
index 4306ff4..3d15f22 100644
--- a/configs/colibri_vf_defconfig
+++ b/configs/colibri_vf_defconfig
@@ -16,6 +16,8 @@
 CONFIG_ENV_VARS_UBOOT_CONFIG=y
 CONFIG_SYS_LOAD_ADDR=0x80008000
 CONFIG_BOOTDELAY=1
+CONFIG_USE_BOOTCOMMAND=y
+CONFIG_BOOTCOMMAND="run ubiboot || run distro_bootcmd;"
 CONFIG_USE_PREBOOT=y
 CONFIG_PREBOOT="setenv fdtfile ${soc}-colibri-${fdt_board}.dtb"
 CONFIG_LOGLEVEL=3