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/at91sam9rlek_nandflash_defconfig b/configs/at91sam9rlek_nandflash_defconfig
index 677c0ae..a922780 100644
--- a/configs/at91sam9rlek_nandflash_defconfig
+++ b/configs/at91sam9rlek_nandflash_defconfig
@@ -19,6 +19,8 @@
 CONFIG_BOOTDELAY=3
 CONFIG_USE_BOOTARGS=y
 CONFIG_BOOTARGS="console=ttyS0,115200 earlyprintk mtdparts=atmel_nand:256k(bootstrap)ro,512k(uboot)ro,256K(env),256k(env_redundant),256k(spare),512k(dtb),6M(kernel)ro,-(rootfs) rootfstype=ubifs ubi.mtd=7 root=ubi0:rootfs"
+CONFIG_USE_BOOTCOMMAND=y
+CONFIG_BOOTCOMMAND="nand read 0x22000000 0x200000 0x600000; nand read 0x21000000 0x180000 0x80000; bootz 0x22000000 - 0x21000000"
 CONFIG_SYS_CONSOLE_IS_IN_ENV=y
 # CONFIG_DISPLAY_BOARDINFO is not set
 CONFIG_HUSH_PARSER=y