Introduce enable in the queue and shaper section in qos config, if
disabled, configuration not done for that instance.
Fixed some bugs in the broadcom.sh script.
Note: The broadcom.sh script has not been updated to take into account
the fact that the board 6846 does not have enough queues available.
This script is kept so for the same of flexibility. The number of queues
per port can be controlled from the uci file now which easily available
and configurable.