[DOC] Update bonding documentation with sysfs info

Bonding documentation needed an update to include sysfs specific
information. This patch adds information on how to change bonding
parameters at runtime using the sysfs interface.
Signed-off-by: NMitch Williams <mitch.a.williams@intel.com>
Signed-off-by: NAuke Kok <auke-jan.h.kok@intel.com>