[CAN]: Fix plain integer definitions in userspace header.

This patch fixes the use of plain integers instead of __u32 in a struct
that is visible from kernel space and user space.

Thanks to Sam Ravnborg for pointing out the wrong plain int usage.

Signed-off-by: Oliver Hartkopp <oliver@hartkopp.net>
Acked-by: Sam Ravnborg <sam@ravnborg.org>
Signed-off-by: David S. Miller <davem@davemloft.net>