[ Upstream commit 9828e6e6 ]

Just use explicit casts, since we really can't change the
types of structures exported to userspace which have been
around for 15 years or so.
Reported-by: Dan Rosenberg <dan.j.rosenberg@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>