mac80211: remove payload alignment warning

The payload alignment warning enabled by MAC80211_DEBUG_PACKET_ALIGNMENT is
difficult. To fix it, a firmware change is needed but in most cases that's
very difficult. So the benefit from the warning is low and most probably
it just creates more confusion for people who just enable all warnings
(like it did for me).

Remove the unaligned IP payload warning and the kconfig option. But
leave the unaligned packet warning, it will be enabled with
MAC80211_VERBOSE_DEBUG.

Signed-off-by: Kalle Valo <kalle.valo@nokia.com>
Signed-off-by: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: John W. Linville <linville@tuxdriver.com>