ath5k: clean up ath5k_hw_set_key

Status: O

With the addition of TKIP (and soon CCMP), key->alg is a more useful
guide to key type than the key length.

This patch cleans up key type assignment in ath5k_hw_set_key by
extracting it into its own function.  It also replaces the separate
memcpy() calls for extracting key material into the hardware format
with a loop that works regardless of key size.

Finally, the patch removes support for WEP-128 since it is a
non-standard key length that mac80211 also doesn't use.

Changes-licensed-under: ISC
Signed-off-by: Bob Copeland <me@bobcopeland.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>