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/r8a779a0_falcon_defconfig b/configs/r8a779a0_falcon_defconfig
index bad5585..4a6006a 100644
--- a/configs/r8a779a0_falcon_defconfig
+++ b/configs/r8a779a0_falcon_defconfig
@@ -18,6 +18,8 @@
 CONFIG_SUPPORT_RAW_INITRD=y
 CONFIG_USE_BOOTARGS=y
 CONFIG_BOOTARGS="root=/dev/nfs rw nfsroot=192.168.0.1:/export/rfs ip=192.168.0.20"
+CONFIG_USE_BOOTCOMMAND=y
+CONFIG_BOOTCOMMAND="tftp 0x48080000 Image; tftp 0x48000000 Image-r8a779a0-falcon.dtb; booti 0x48080000 - 0x48000000"
 CONFIG_DEFAULT_FDT_FILE="r8a779a0-falcon.dtb"
 CONFIG_HUSH_PARSER=y
 CONFIG_CMD_BOOTZ=y