of/Kconfig: Spelling s/one/once/

Signed-off-by: Geert Uytterhoeven <geert+renesas@linux-m68k.org>
Signed-off-by: Rob Herring <robh@kernel.org>

drivers/of/Kconfig

@@ -20,7 +20,7 @@ config OF_SELFTEST
 	depends on OF_IRQ
 	help
 	  This option builds in test cases for the device tree infrastructure
-	  that are executed one at boot time, and the results dumped to the
+	  that are executed once at boot time, and the results dumped to the
 	  console.
 
 	  If unsure, say N here, but this option is safe to enable.