IB/rxe: Enable type checking on SKB_TO_PKT() and PKT_TO_SKB() arguments

Let the compiler check the type of the arguments passed to SKB_TO_PKT()
and PKT_TO_SKB().

Signed-off-by: Bart Van Assche <bart.vanassche@sandisk.com>
Reviewed-by: Leon Romanovsky <leonro@mellanox.com>
Reviewed-by: Andrew Boyer <andrew.boyer@dell.com>
Cc: Moni Shoua <monis@mellanox.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>