net: dsa: make dsa_pack_type static

net/dsa/dsa.c:624:20: sparse: symbol 'dsa_pack_type' was not declared.
Should it be static?

Fixes: 3e8a72d1 ("net: dsa: reduce number of protocol hooks")
Signed-off-by: Fengguang Wu <fengguang.wu@intel.com>
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>