sfc: fix use-after-free in efx_tc_flower_record_encap_match()

When writing error messages to extack for pseudo collisions, we can't
 use encap->type as encap has already been freed.  Fortunately the
 same value is stored in local variable em_type, so use that instead.

Fixes: 3c9561c0 ("sfc: support TC decap rules matching on enc_ip_tos")
Reported-by: Simon Horman <simon.horman@corigine.com>
Signed-off-by: Edward Cree <ecree.xilinx@gmail.com>
Reviewed-by: Simon Horman <simon.horman@corigine.com>
Signed-off-by: David S. Miller <davem@davemloft.net>