x86: zboot: Move command code into its own file

Much of the code in zimage.c deals with the zboot command. Move it into
a sepatate zboot.c file within the cmd/ directory. This will eventually
allow use of the zimage logic without the command being enabled.

Signed-off-by: Simon Glass <sjg@chromium.org>

arch/x86/include/asm/zimage.h

@@ -71,6 +71,37 @@ struct zboot_state {
 
 extern struct zboot_state state;
 
+/**
+ * zimage_dump() - Dump information about a zimage
+ *
+ * @base_ptr: Pointer to the boot parameters
+ * @show_cmdline: true to show the kernel command line
+ */
+void zimage_dump(struct boot_params *base_ptr, bool show_cmdline);
+
+/**
+ * zboot_load() - Load a zimage
+ *
+ * Load the zimage into the correct place
+ *
+ * Return: 0 if OK, -ve on error
+ */
+int zboot_load(void);
+
+/**
+ * zboot_setup() - Set up the zboot image reeady for booting
+ *
+ * Return: 0 if OK, -ve on error
+ */
+int zboot_setup(void);
+
+/**
+ * zboot_go() - Start the image
+ *
+ * Return: 0 if OK, -ve on error
+ */
+int zboot_go(void);
+
 /**
  * load_zimage() - Load a zImage or bzImage
  *