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_mmc_defconfig b/configs/at91sam9rlek_mmc_defconfig
index c8bb88e..9fd2042 100644
--- a/configs/at91sam9rlek_mmc_defconfig
+++ b/configs/at91sam9rlek_mmc_defconfig
@@ -19,6 +19,8 @@
 CONFIG_BOOTDELAY=3
 CONFIG_USE_BOOTARGS=y
 CONFIG_BOOTARGS="console=ttyS0,115200 mtdparts=atmel_nand:8M(bootstrap/uboot/kernel)ro,-(rootfs) root=/dev/mmcblk0p2 rw rootwait"
+CONFIG_USE_BOOTCOMMAND=y
+CONFIG_BOOTCOMMAND="fatload mmc 0:1 0x21000000 at91sam9rlek.dtb; fatload mmc 0:1 0x22000000 zImage; bootz 0x22000000 - 0x21000000"
 CONFIG_SYS_CONSOLE_IS_IN_ENV=y
 # CONFIG_DISPLAY_BOARDINFO is not set
 CONFIG_HUSH_PARSER=y