bridge: mdb: Add source list support

bridge: mdb: Add source list support

Allow user space to specify the source list of (*, G) entries by adding
the 'MDBE_ATTR_SRC_LIST' attribute to the 'MDBA_SET_ENTRY_ATTRS' nest.

Example:

 # bridge mdb add dev br0 port dummy10 grp 239.1.1.1 temp source_list 198.51.100.1,198.51.100.2 filter_mode exclude

 # bridge -d -s mdb show
 dev br0 port dummy10 grp 239.1.1.1 src 198.51.100.2 temp filter_mode include proto static  blocked    0.00
 dev br0 port dummy10 grp 239.1.1.1 src 198.51.100.1 temp filter_mode include proto static  blocked    0.00
 dev br0 port dummy10 grp 239.1.1.1 temp filter_mode exclude source_list 198.51.100.2/0.00,198.51.100.1/0.00 proto static   256.42

 # bridge -j -p -d -s mdb show
 [ {
         "mdb": [ {
                 "index": 10,
                 "dev": "br0",
                 "port": "dummy10",
                 "grp": "239.1.1.1",
                 "src": "198.51.100.2",
                 "state": "temp",
                 "filter_mode": "include",
                 "protocol": "static",
                 "flags": [ "blocked" ],
                 "timer": "   0.00"
             },{
                 "index": 10,
                 "dev": "br0",
                 "port": "dummy10",
                 "grp": "239.1.1.1",
                 "src": "198.51.100.1",
                 "state": "temp",
                 "filter_mode": "include",
                 "protocol": "static",
                 "flags": [ "blocked" ],
                 "timer": "   0.00"
             },{
             },{
                 "index": 10,
                 "dev": "br0",
                 "port": "dummy10",
                 "grp": "239.1.1.1",
                 "state": "temp",
                 "filter_mode": "exclude",
                 "source_list": [ {
                         "address": "198.51.100.2",
                         "timer": "0.00"
                     },{
                         "address": "198.51.100.1",
                         "timer": "0.00"
                     } ],
                 "protocol": "static",
                 "flags": [ ],
                 "timer": " 251.19"
             } ],
         "router": {}
     } ]

Signed-off-by: Ido Schimmel <idosch@nvidia.com>
Reviewed-by: Nikolay Aleksandrov <razor@blackwall.org>
Signed-off-by: David Ahern <dsahern@kernel.org>