lib,rlc_am_nr: fix buffer state checker in rx status report with ranges test

lib/test/rlc/rlc_am_nr_test.cc

@@ -2552,7 +2552,8 @@ int rx_nack_range_test(rlc_am_nr_sn_size_t sn_size)
   rlc_am_nr_write_status_pdu(status, sn_size, &status_pdu);
 
   rlc1.write_pdu(status_pdu.msg, status_pdu.N_bytes);
-  TESTASSERT_EQ(0, rlc1.get_buffer_state());
+
+  TESTASSERT_EQ(2 * pdu_size_first + 3 * pdu_size_continued, rlc1.get_buffer_state());
   return SRSRAN_SUCCESS;
 }