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/r8a77990_ebisu_defconfig b/configs/r8a77990_ebisu_defconfig
index 0c1e5a1..d41385b 100644
--- a/configs/r8a77990_ebisu_defconfig
+++ b/configs/r8a77990_ebisu_defconfig
@@ -15,6 +15,8 @@
 CONFIG_FIT=y
 CONFIG_SUPPORT_RAW_INITRD=y
 CONFIG_USE_BOOTARGS=y
+CONFIG_USE_BOOTCOMMAND=y
+CONFIG_BOOTCOMMAND="tftp 0x48080000 Image; tftp 0x48000000 Image-r8a77990-ebisu.dtb; booti 0x48080000 - 0x48000000"
 CONFIG_DEFAULT_FDT_FILE="r8a77990-ebisu.dtb"
 # CONFIG_BOARD_EARLY_INIT_F is not set
 CONFIG_UPDATE_TFTP=y