driver-core: platform: fix typo in documentation for multi-driver helper

The function name in the documentation lacked an 's'. Add it.

Fixes: dbe2256ddd8e ("driver-core: platform: Provide helpers for multi-driver modules")
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Acked-by: Thierry Reding <treding@nvidia.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Documentation/driver-model/platform.txt

@@ -75,7 +75,7 @@ If one of the drivers fails to register, all drivers registered up to that
 point will be unregistered in reverse order. Note that there is a convenience
 macro that passes THIS_MODULE as owner parameter:
 
-	#define platform_register_driver(drivers, count)
+	#define platform_register_drivers(drivers, count)
 
 
 Device Enumeration