netdevice: Support DSA tagging when DSA is built as a module

This change corrects an error seen when DSA tagging is built as a module.
Without this change it is not possible to get XDSA tagged frames as the
test for tagging is stripped by the #ifdef check.

Signed-off-by: Alexander Duyck <alexander.h.duyck@intel.com>
Acked-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>