xdp: remove redundant argument to trace_xdp_redirect

Supplying the action argument XDP_REDIRECT to the tracepoint xdp_redirect
is redundant as it is only called in-case this action was specified.

Remove the argument, but keep "act" member of the tracepoint struct and
populate it with XDP_REDIRECT.  This makes it easier to write a common bpf_prog
processing events.

Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>