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/ls1043ardb_sdcard_defconfig b/configs/ls1043ardb_sdcard_defconfig
index ba0b2cd..05cb940 100644
--- a/configs/ls1043ardb_sdcard_defconfig
+++ b/configs/ls1043ardb_sdcard_defconfig
@@ -30,6 +30,7 @@
 CONFIG_BOOTDELAY=10
 CONFIG_USE_BOOTARGS=y
 CONFIG_BOOTARGS="console=ttyS0,115200 root=/dev/ram0 earlycon=uart8250,mmio,0x21c0500 mtdparts=60000000.nor:2m@0x100000(nor_bank0_uboot),40m@0x1100000(nor_bank0_fit),7m(nor_bank0_user),2m@0x4100000(nor_bank4_uboot),40m@0x5100000(nor_bank4_fit),-(nor_bank4_user);7e800000.flash:1m(nand_uboot),1m(nand_uboot_env),20m(nand_fit);spi0.0:1m(uboot),5m(kernel),1m(dtb),9m(file_system)"
+CONFIG_BOOTCOMMAND="run distro_bootcmd; run sd_bootcmd; env exists secureboot && esbc_halt;"
 CONFIG_MISC_INIT_R=y
 CONFIG_SPL_FSL_PBL=y
 CONFIG_SPL_BOARD_INIT=y