USB: xhci: No GFP_KERNEL in block error handling

xhci_add_endpoint() is used in the reset path. It must
use GFP_NOIO to avoid a possible deadlock.

Signed-off-by: Oliver Neukum <oliver@neukum.org>
Acked-by: Sarah Sharp <sarah.a.sharp@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>