examples/dvbininfo/libdvbpsi.c: Free ALL pmt's.

The p_prev->p_next was never set to NULL, but instead the p_pmt->p_next pointer was.
This resulted in never freeing additional PMT entries from the PAT.

examples/dvbinfo/libdvbpsi.c

@@ -1666,8 +1666,8 @@ void libdvbpsi_exit(ts_stream_t *stream)
        stream->i_pmt--;
        p_prev = p_pmt;
        p_pmt = p_pmt->p_next;
-       if (p_pmt)
-           p_pmt->p_next = NULL;
+       if (p_prev)
+           p_prev->p_next = NULL;
        free(p_prev);
    }