rt2x00: Remove intf->bssid field.

The bssid field in struct rt2x00_intf is only written to once, and is
never read from.

Remove this field, as it appears to not be needed.

Signed-off-by: Gertjan van Wingerde <gwingerde@gmail.com>
Signed-off-by: Ivo van Doorn <IvDoorn@gmail.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>