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/socrates_defconfig b/configs/socrates_defconfig
index 72c0717..34d84b5 100644
--- a/configs/socrates_defconfig
+++ b/configs/socrates_defconfig
@@ -10,6 +10,8 @@
 CONFIG_FIT_VERBOSE=y
 CONFIG_OF_BOARD_SETUP=y
 CONFIG_BOOTDELAY=1
+CONFIG_USE_BOOTCOMMAND=y
+CONFIG_BOOTCOMMAND="run boot_nor"
 CONFIG_USE_PREBOOT=y
 CONFIG_PREBOOT="echo;echo Welcome on the ABB Socrates Board;echo"
 CONFIG_SYS_CONSOLE_IS_IN_ENV=y