net: tap: check vlan with eth_type_vlan() method

[ Upstream commit b69df2608281b71575fbb3b9f426dbcc4be8a700 ]

Replace some checks for ETH_P_8021Q and ETH_P_8021AD in
drivers/net/tap.c with eth_type_vlan.

Signed-off-by: Menglong Dong <dong.menglong@zte.com.cn>
Link: https://lore.kernel.org/r/20210115023238.4681-1-dong.menglong@zte.com.cn


Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Stable-dep-of: 4063384ef762 ("net: add vlan_get_protocol_and_depth() helper")
Signed-off-by: Sasha Levin <sashal@kernel.org>