bootstd: Introduce programmatic boot

At present bootstd requires CONFIG_CMDLINE to operate. Add a new
'programmatic' boot which can be used when no command line is available.
For now it does almost nothing, since most bootmeths require the
command line.

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

include/bootstd.h

@@ -94,4 +94,13 @@ int bootstd_get_priv(struct bootstd_priv **stdp);
  */
 void bootstd_clear_glob(void);
 
+/**
+ * bootstd_prog_boot() - Run standard boot in a fully programmatic mode
+ *
+ * Attempts to boot without making any use of U-Boot commands
+ *
+ * Returns: -ve error value (does not return except on failure to boot)
+ */
+int bootstd_prog_boot(void);
+
 #endif