license.bbclass: Added function get_deployed_dependencies

license.bbclass: Added function get_deployed_dependencies

This change introduce a new function to get the dependencies
that were deployed. It uses BB_TASKDEPDATAto get all the
dependencies of the current task, so it is possible to get
different packages depending at what point this function is
called.

[YOCTO #6772]

(From OE-Core rev: 2be96279580eac2b03970131dcd81b13c7f7f7d5)

Signed-off-by: Mariano Lopez <mariano.lopez@linux.intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>