bridge: support sending rntl info when we set attributes through sysfs/ioctl

This patchset is used to support sending rntl info to user in some places, and ensure that whenever those attributes change internally or from sysfs, that a netlink notification is sent out to listeners.

It also make some adjustment in bridge sysfs so that we can implement this easily.

I've done some tests on this patchset, like:
[br_sysfs]
1. change all the attribute values of br or brif:

  $ echo $value > /sys/class/net/br0/bridge/{*}
  $ echo $value > /sys/class/net/br0/brif/eth1/{*}

2. meanwhile, on another terminal to observe the msg:

  $ bridge monitor

[br_ioctl]
1. in bridge-utils package, do some changes in br_set, let brctl command use ioctl to set attribute:

         if ((ret = set_sysfs(path, value)) < 0) { -->
         if (1) {

  $ brctl set*

2. meanwhile, on another terminal to observe the msg:

  $ bridge monitor

This test covers all the attributes that brctl and sysfs support to set.

Xin Long (6):
bridge: simplify the flush_store by calling store_bridge_parm
bridge: simplify the forward_delay_store by calling store_bridge_parm
bridge: simplify the stp_state_store by calling store_bridge_parm
bridge: a netlink notification should be sent when those attributes
are changed by br_sysfs_br
bridge: a netlink notification should be sent when those attributes
are changed by br_sysfs_if
bridge: a netlink notification should be sent when those attributes
are changed by ioctl

 net/bridge/br_ioctl.c    | 40 ++++++++++++++---------
 net/bridge/br_sysfs_br.c | 84 ++++++++++++++++++++----------------------------
 net/bridge/br_sysfs_if.c |  5 +--
 net/bridge/br_vlan.c     | 30 +++--------------
 4 files changed, 66 insertions(+), 93 deletions(-)

2.1.0