IB/rxe: Remove unneeded cast in rxe_srq_from_attr()

It makes me nervous when we cast pointer parameters.  I would estimate
that around 50% of the time, it indicates a bug.  Here the cast is not
needed becaue u32 and and unsigned int are the same thing.  Removing the
cast makes the code more robust and future proof in case any of the
types change.

Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Reviewed-by: Leon Romanovsky <leonro@mellanox.com>
Reviewed-by: Yuval Shaia <yuval.shaia@oracle.com>
Acked-by: Moni Shoua <monis@mellanox.com>
Reviewed-by: Yuval Shaia <yuval.shaia@oracle.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>