drivers/net/bonding: fix sparse warnings: move decls to header file

Fix this sparse warnings:

  drivers/net/bonding/bond_main.c:104:20: warning: symbol 'bonding_defaults' was not declared. Should it be static?
  drivers/net/bonding/bond_main.c:204:22: warning: symbol 'ad_select_tbl' was not declared. Should it be static?
  drivers/net/bonding/bond_sysfs.c:60:21: warning: symbol 'bonding_rwsem' was not declared. Should it be static?

Signed-off-by: Hannes Eder <hannes@hanneseder.net>
Signed-off-by: David S. Miller <davem@davemloft.net>