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/trats2_defconfig b/configs/trats2_defconfig
index 60e7e2c..9fb6ba7 100644
--- a/configs/trats2_defconfig
+++ b/configs/trats2_defconfig
@@ -16,7 +16,7 @@
 CONFIG_FIT_VERBOSE=y
 CONFIG_USE_BOOTARGS=y
 CONFIG_BOOTARGS="Please use defined boot"
-# CONFIG_USE_BOOTCOMMAND is not set
+CONFIG_BOOTCOMMAND="run autoboot"
 CONFIG_SYS_CONSOLE_IS_IN_ENV=y
 CONFIG_SYS_CONSOLE_INFO_QUIET=y
 CONFIG_MISC_INIT_R=y