[PATCH] USB Storage: fix compile error

This patch fixes a compiler error caused by a missing prototype.  It should
apply directly to Greg KH's usb-2.6.git tree.

Signed-off-by: Matthew Dharm <mdharm-usb@one-eyed-alien.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>