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/da850evm_defconfig b/configs/da850evm_defconfig
index 33d1cf3..8437a27 100644
--- a/configs/da850evm_defconfig
+++ b/configs/da850evm_defconfig
@@ -25,6 +25,8 @@
 CONFIG_SYS_LOAD_ADDR=0xc0700000
 CONFIG_SYS_EXTRA_OPTIONS="MAC_ADDR_IN_SPIFLASH"
 CONFIG_BOOTDELAY=3
+CONFIG_USE_BOOTCOMMAND=y
+CONFIG_BOOTCOMMAND="run envboot; run mmcboot; "
 CONFIG_DEFAULT_FDT_FILE="da850-evm.dtb"
 # CONFIG_DISPLAY_CPUINFO is not set
 # CONFIG_DISPLAY_BOARDINFO is not set