Convert CONFIG_CMD_SH_ZIMAGEBOOT to Kconfig

This converts the following to Kconfig:
   CONFIG_CMD_SH_ZIMAGEBOOT

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
Reviewed-by: Philipp Tomsich <philipp.tomsich@theobroma-systems.com>
diff --git a/arch/sh/lib/Kconfig b/arch/sh/lib/Kconfig
new file mode 100644
index 0000000..cec8d09
--- /dev/null
+++ b/arch/sh/lib/Kconfig
@@ -0,0 +1,6 @@
+config CMD_SH_ZIMAGEBOOT
+	bool "zimageboot - Boot a zImage on SH"
+	default y
+	help
+	  This is special SH-specific command to boot a zImage (compressed
+	  Linux image) on SH-architecture boards.