[MAC80211]: rework key handling

[MAC80211]: rework key handling

This moves all the key handling code out from ieee80211_ioctl.c
into key.c and also does the following changes including documentation
updates in mac80211.h:

 1) Turn off hardware acceleration for keys when the interface
    is down. This is necessary because otherwise monitor
    interfaces could be decrypting frames for other interfaces
    that are down at the moment. Also, it should go some way
    towards better suspend/resume support, in any case the
    routines used here could be used for that as well.
    Additionally, this makes the driver interface nicer, keys
    for a specific local MAC address are only ever present
    while an interface with that MAC address is enabled.

 2) Change driver set_key() callback interface to allow only
    return values of -ENOSPC, -EOPNOTSUPP and 0, warn on all
    other return values. This allows debugging the stack when
    a driver notices it's handed a key while it is down.

 3) Invert the flag meaning to KEY_FLAG_UPLOADED_TO_HARDWARE.

 4) Remove REMOVE_ALL_KEYS command as it isn't used nor do we
    want to use it, we'll use DISABLE_KEY for each key. It is
    hard to use REMOVE_ALL_KEYS because we can handle multiple
    virtual interfaces with different key configuration, so we'd
    have to keep track of a lot of state for this and that isn't
    worth it.

 5) Warn when disabling a key fails, it musn't.

 6) Remove IEEE80211_HW_NO_TKIP_WMM_HWACCEL in favour of per-key
    IEEE80211_KEY_FLAG_WMM_STA to let driver sort it out itself.

 7) Tell driver that a (non-WEP) key is used only for transmission
    by using an all-zeroes station MAC address when configuring.

 8) Change the set_key() callback to have access to the local MAC
    address the key is being added for.

Signed-off-by: Johannes Berg <johannes@sipsolutions.net>
Acked-by: Michael Wu <flamingice@sourmilk.net>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
Signed-off-by: David S. Miller <davem@davemloft.net>