vlan: TCI related type and naming cleanups

The VLAN code contains multiple spots that use tag, id and tci as
identifiers for arguments and variables incorrectly and they actually
contain or are expected to contain something different. Additionally
types are used inconsistently (unsigned short vs u16) and identifiers
are sometimes capitalized.

- consistently use u16 for storing TCI, ID or QoS values
- consistently use vlan_id and vlan_tci for storing the respective values
- remove capitalization
- add kdoc comment to netif_hwaccel_{rx,receive_skb}

Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>