gst1-plugins-bad: conditionally add gpl license

gst1-plugins-bad: conditionally add gpl license

Currently, GST1_PLUGINS_BAD_LICENSE_FILES starts out set to
both the GPL COPYING file and the LGPL COPYING.LIB file, but
the GST1_PLUGINS_BAD_LICENSE handling only claims LGPL, and
then intelligently adds GPL if needed.  This change moves the
GPL file addition to the same conditional clause so that the
GPL file is included in the legal-info location only if GPL
code is actually used.

Signed-off-by: Danomi Manchego <danomimanchego123@gmail.com>
Reviewed-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>