batman-adv: Use the mac80211 compat layer

batman-adv: Use the mac80211 compat layer

BATMAN_V (in the upcoming release) will use structures from the mac80211
package. These structures can be incompatible to the structures defined in
the header of the kernel. This can lead to weird problems like stack
overflows or memory corruptions.

To avoid this, the batman-adv has to be compiled against the mac80211
headers instead of the kernel headers. But this requires that the
compatibility headers of compat-wireless are used. So the batman-adv
compatibility layer has (mostly) be removed and instead the
compat-wireless/mac80211 compat layer has to be used.

Signed-off-by: Sven Eckelmann <sven@narfation.org>