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/ds109_defconfig b/configs/ds109_defconfig
index d7e8651..c5a707c 100644
--- a/configs/ds109_defconfig
+++ b/configs/ds109_defconfig
@@ -17,6 +17,8 @@
 CONFIG_DEFAULT_DEVICE_TREE="kirkwood-ds109"
 # CONFIG_SYS_MALLOC_F is not set
 CONFIG_SYS_LOAD_ADDR=0x800000
+CONFIG_USE_BOOTCOMMAND=y
+CONFIG_BOOTCOMMAND="setenv ethact egiga0; ${x_bootcmd_ethernet}; ${x_bootcmd_usb}; ${x_bootcmd_kernel}; setenv bootargs ${x_bootargs} ${x_bootargs_root}; bootm 0x6400000;"
 CONFIG_USE_PREBOOT=y
 CONFIG_HUSH_PARSER=y
 # CONFIG_CMD_FLASH is not set