net/mlx5e: Report mlx5e_xdp_set errors

If the channels fail to reopen after setting an XDP program, return the
error code instead of 0. A proper fix is still needed, as now any error
while reopening the channels brings the interface down. This patch only
adds error reporting.

Signed-off-by: Maxim Mikityanskiy <maximmi@mellanox.com>
Reviewed-by: Tariq Toukan <tariqt@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>