cmd: booti: move CONFIG_CMD_BOOTI to Kconfig

This command is used to boot ARM64 Linux.

I made DISTRO_DEFAULTS select this option for ARM64 to respect
include/config_distro_defaults.h.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/cmd/Kconfig b/cmd/Kconfig
index d69b817..e219246 100644
--- a/cmd/Kconfig
+++ b/cmd/Kconfig
@@ -165,6 +165,13 @@
 	help
 	  Boot the Linux zImage
 
+config CMD_BOOTI
+	bool "booti"
+	depends on ARM64
+	default y
+	help
+	  Boot an AArch64 Linux Kernel image from memory.
+
 config CMD_BOOTEFI
 	bool "bootefi"
 	depends on EFI_LOADER