libdvbv5: add a missing return

libdvbv5: add a missing return

Changeset 0097e30 fixed a Coverity bug that were causing a
memory leak in the case that the DVB dummy logic happens.
However, I forgot to add a return there, causing another
bug, also reported by Coverity:

*** CID 1233758:  Use after free  (USE_AFTER_FREE)
/lib/libdvbv5/descriptors.c: 81 in dvb_desc_default_print()
75     {
76     	if (!parms) {
77     		parms = dvb_fe_dummy();
78     		dvb_hexdump(parms, "|           ", desc->data, desc->length);
79     		free(parms);
80     	}

Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>