bonding: make a generic sysfs option store and fix comments

Introduce a generic option store function for sysfs and remove the
specific ones. The attribute name is used to match against the option
which is to be set.
Also adjust the "name" of tlb_dynamic_lb option to match the sysfs
entry and fix the comments and comment style in bond_sysfs.c
The comments which showed obvious behaviour (i.e. behaviour that's seen
in the option's entry) are removed, the ones that explained important
points about the setting function have been moved above the respective
set function in bond_options.c

There's only 1 exception: num_unsol_na/num_grat_arp since it has 2 names

CC: Jay Vosburgh <j.vosburgh@gmail.com>
CC: Veaceslav Falico <vfalico@gmail.com>
CC: Andy Gospodarek <andy@greyhouse.net>
CC: David S. Miller <davem@davemloft.net>

Signed-off-by: Nikolay Aleksandrov <nikolay@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>