IB/rxe: Remove an unused variable and an unused argument

The variable 'av' is not used so remove it. Since that change
removes the last user of the 'wqe' argument, remove that argument
too.

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