license.bbclass: do not process LICENSE_pn variables
The loop iterating over LICENSE_pn variables has never worked. In
addition, the LICENSE variable is supposed to contain all licenses
defined in LICENSE_pn variables. Thus, it is simpler just to use LICENSE
as the data we get is essentially the same.
[YOCTO #9499]
Signed-off-by: Markus Lehtonen <markus.lehtonen@linux.intel.com> Signed-off-by: Ross Burton <ross.burton@intel.com>