Documentation: Document of_overlay_disable parameter

Document the of_overlay_disable parameter.

Signed-off-by: Pantelis Antoniou <pantelis.antoniou@konsulko.com>
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>

Author: pantoniou

Documentation/admin-guide/kernel-parameters.txt

@@ -4025,6 +4025,8 @@
 			This can be set from sysctl after boot.
 			See Documentation/admin-guide/sysctl/vm.rst for details.
 
+	of_overlay_disable	[OF] Disable device tree overlays at boot time.
+
 	ohci1394_dma=early	[HW] enable debugging via the ohci1394 driver.
 			See Documentation/core-api/debugging-via-ohci1394.rst for more
 			info.