bootstd: Allow storing the OS command line in the bootflow

Some operating systems have a command line which can be adjusted before
booting. Store this in the bootflow so it can be controlled within
U-Boot.

Fix up the example output while we are here, since there are a few new
items.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>

include/bootflow.h

@@ -81,6 +81,7 @@ enum bootflow_flags_t {
  * @fdt_size: Size of FDT file
  * @fdt_addr: Address of loaded fdt
  * @flags: Flags for the bootflow (see enum bootflow_flags_t)
+ * @cmdline: OS command line, or NULL if not known (allocated)
  */
 struct bootflow {
 	struct list_head bm_node;
@@ -104,6 +105,7 @@ struct bootflow {
 	int fdt_size;
 	ulong fdt_addr;
 	int flags;
+	char *cmdline;
 };
 
 /**