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/controlcenterdc_defconfig b/configs/controlcenterdc_defconfig
index 13f093f..44db311 100644
--- a/configs/controlcenterdc_defconfig
+++ b/configs/controlcenterdc_defconfig
@@ -26,6 +26,8 @@
 CONFIG_FIT=y
 CONFIG_FIT_SIGNATURE=y
 CONFIG_FIT_VERBOSE=y
+CONFIG_USE_BOOTCOMMAND=y
+CONFIG_BOOTCOMMAND="if env exists keyprogram; then; setenv keyprogram; run nfsboot; fi; run dobootfail"
 CONFIG_USE_PREBOOT=y
 CONFIG_SYS_CONSOLE_INFO_QUIET=y
 CONFIG_DISPLAY_BOARDINFO_LATE=y