[PATCH] usbcore: Use kzalloc instead of kmalloc/memset

This patch (as590) fixes up all the remaining places where usbcore can
use kzalloc rather than kmalloc/memset.

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>