doc: adding definitions for load default params mgmt op

doc: adding definitions for load default params mgmt op

This change adds the definition for the read/set default parameter
commands.

In particular, these commands are used to read and set the system
default parameters.  The use of a TLV format also ensures that
parameters are expandable in the future.

This will allow bluetoothd to load parameters from a conf file that may
be customized for the specific requirements of each platforms.

Signed-off-by: Anuj Jain <anuj01.jain@samsung.com>
Signed-off-by: Ayush Garg <ayush.garg@samsung.com>