staging: rt2870: Add USB ID for Belkin F6D4050 v2

Device missing from current tables.

Signed-off-by: Larry Finger <Larry.Finger@lwfinger.net>
Tested-by: Rod Huffaker <rod.huffaker@gmail.com>
Cc: Stable <stable@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>