bonding: add all_slaves_active parameter

v2: changed parameter name from 'keep_all' to 'all_slaves_active' and
skipped setting slaves to inactive rather than creating a new flag at
Jay's suggestion.

In an effort to suppress duplicate frames on certain bonding modes
(specifically the modes that do not require additional configuration on
the switch or switches connected to the host), code was added in the
generic receive patch in 2.6.16.  The current behavior works quite well
for most users, but there are some times it would be nice to restore old
functionality and allow all frames to make their way up the stack.

This patch adds support for a new module option and sysfs file called
'all_slaves_active' that will restore pre-2.6.16 functionality if the
user desires.  The default value is '0' and retains existing behavior,
but the user can set it to '1' and allow all frames up if desired.

Signed-off-by: Andy Gospodarek <andy@greyhouse.net>
Signed-off-by: Jay Vosburgh <fubar@us.ibm.com>
Signed-off-by: Neil Horman <nhorman@tuxdriver.com>
Signed-off-by: David S. Miller <davem@davemloft.net>