loader: Add loader_menu

If set to 'none' then the menu isn't displayed.
The 'brand' and 'logo' part are stil displayed.

Differential Revision:	https://reviews.freebsd.org/D49820
Reviewed by:	imp, kevans
Sponsored by:	Beckhoff Automation GmbH & Co. KG

stand/defaults/loader.conf.5

@@ -424,6 +424,10 @@ Possible values are:
 .Dq Li beastie ,
 and
 .Dq Li none .
+.It Va loader_menu
+If set to
+.Dq NONE ,
+the menu will not be displayed
 .It Va loader_color
 If set to
 .Dq NO ,

stand/lua/drawer.lua

@@ -166,6 +166,10 @@ local function drawmenu(menudef)
 	local x = menu_position.x
 	local y = menu_position.y
 
+	if string.lower(loader.getenv("loader_menu") or "") == "none" then
+	   return
+	end
+
 	x = x + shift.x
 	y = y + shift.y
 
@@ -276,6 +280,10 @@ local function drawbox()
 	local menu_header_align = loader.getenv("loader_menu_title_align")
 	local menu_header_x
 
+	if string.lower(loader.getenv("loader_menu") or "") == "none" then
+	   return
+	end
+
 	x = x + shift.x
 	y = y + shift.y