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/usbarmory_defconfig b/configs/usbarmory_defconfig
index d70b9cf..727720c 100644
--- a/configs/usbarmory_defconfig
+++ b/configs/usbarmory_defconfig
@@ -15,7 +15,7 @@
 # CONFIG_CMD_BMODE is not set
 CONFIG_DISTRO_DEFAULTS=y
 CONFIG_SYS_LOAD_ADDR=0x72000000
-# CONFIG_USE_BOOTCOMMAND is not set
+CONFIG_BOOTCOMMAND="run distro_bootcmd; setenv bootargs console=${console} ${bootargs_default}; ext2load mmc 0:1 ${kernel_addr_r} /boot/zImage; ext2load mmc 0:1 ${fdt_addr_r} /boot/${fdtfile}; bootz ${kernel_addr_r} - ${fdt_addr_r}"
 CONFIG_CMD_MEMTEST=y
 CONFIG_CMD_FUSE=y
 CONFIG_CMD_I2C=y