devlink: Fix dmac_filter trap name, align to its documentation

%s/dest_mac_filter/dmac_filter/g

Fixes: e78ab164

 ("devlink: Add DMAC filter generic packet trap")
Signed-off-by: Aya Levin <ayal@nvidia.com>
Reported-by: Ido Schimmel <idosch@nvidia.com>
Reviewed-by: Tariq Toukan <tariqt@nvidia.com>
Reviewed-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>