bonding: document undocumented active_slave sysfs entry.
bonding: document undocumented active_slave sysfs entry.

v2, based on Jay's review.

I kept the 'link must be up' part, because this is enforced in the code.

Signed-off-by: Nicolas de Pesloüan <a3380c81fd3de0cead1f530bf66f35d8fd661ef2@free.fr>
Signed-off-by: Jay Vosburgh <9ab50f27d4201db9b28483ba83c48ebafbb2aa17@us.ibm.com>
cc: Andy Gospodarek <e3579b1e47f273529f0f929453e939a68ede9fd1@greyhouse.net>
Signed-off-by: David S. Miller <fe08d3c717adf2ae63592e4c9aec6e3e404d8e3e@davemloft.net>

TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs