env: Move the doc comment to the code

This doesn't really make much sense in the documentation. Add a code
comment instead.
Suggested-by: NHeinrich Schuchardt <xypron.glpk@gmx.de>
Signed-off-by: NSimon Glass <sjg@chromium.org>

common/autoboot.c

@@ -446,6 +446,11 @@ const char *bootdelay_process(void)
 	s = env_get("bootdelay");
 	bootdelay = s ? (int)simple_strtol(s, NULL, 10) : CONFIG_BOOTDELAY;
 
+	/*
+	 * Does it really make sense that the devicetree overrides the user
+	 * setting? It is possibly helpful for security since the device tree
+	 * may be signed whereas the environment is often loaded from storage.
+	 */
 	if (IS_ENABLED(CONFIG_OF_CONTROL))
 		bootdelay = ofnode_conf_read_int("bootdelay", bootdelay);
 

doc/usage/environment.rst

@@ -120,7 +120,6 @@ bootdelay
     The default value is defined by CONFIG_BOOTDELAY.
     The value of 'bootdelay' is overridden by the /config/bootdelay value in
     the device-tree if CONFIG_OF_CONTROL=y.
-    Does it really make sense that the devicetree overrides the user setting?
 
 bootcmd
     The command that is run if the user does not enter the shell during the