mac80211: Honor SW_CRYPTO_CONTROL for unicast keys in AP VLAN mode

Restore SW_CRYPTO_CONTROL operation on AP_VLAN interfaces for unicast
keys, the original override was intended to be done for group keys as
those are treated specially by mac80211 and would always have been
rejected.

Now the situation is that AP_VLAN support must be enabled by the driver
if it can support it (meaning it can support software crypto GTK TX).

Thus, also simplify the code - if we get here with AP_VLAN and non-
pairwise key, software crypto must be used (driver doesn't know about
the interface) and can be used (driver must've advertised AP_VLAN if
it also uses SW_CRYPTO_CONTROL).

Fixes: db3bdcb9 ("mac80211: allow AP_VLAN operation on crypto controlled devices")
Signed-off-by: Alexander Wetzel <alexander@wetzel-home.de>
[rewrite commit message]
Signed-off-by: Johannes Berg <johannes.berg@intel.com>