a_iface: Fix hexdumping of N-DATA.req

For some reason the existing code was using msgb_hexdump_l2() while the
L2 header is not used by the BSSAP transmit code.  Let's fix this.

Change-Id: I52a1eb3a867ece63fcfa4c2a720d035ebfb90a7b
diff --git a/tests/msc_vlr/msc_vlr_test_gsm_ciph.err b/tests/msc_vlr/msc_vlr_test_gsm_ciph.err
index 2fb9bd8..ef77391 100644
--- a/tests/msc_vlr/msc_vlr_test_gsm_ciph.err
+++ b/tests/msc_vlr/msc_vlr_test_gsm_ciph.err
@@ -2452,7 +2452,7 @@
 DVLR vlr_lu_fsm(IMSI-901700000004620:GERAN-A-0:LU){VLR_ULA_S_WAIT_AUTH}: Set Ciphering Mode
 DMM IMSI-901700000004620: to determine whether A5/3 is supported, first ask for a Classmark Update to obtain Classmark 2
 DBSSAP RAN_conn(IMSI-901700000004620:GERAN-A-0:LU){RAN_CONN_S_AUTH_CIPH}: Tx BSSMAP CLASSMARK REQUEST to BSC
-DBSSAP RAN_conn(IMSI-901700000004620:GERAN-A-0:LU){RAN_CONN_S_AUTH_CIPH}: N-DATA.req([])
+DBSSAP RAN_conn(IMSI-901700000004620:GERAN-A-0:LU){RAN_CONN_S_AUTH_CIPH}: N-DATA.req(00 01 58 )
   BSC <--BSSAP-BSS-MANAGEMENT-- MSC: CLASSMARK REQ [L3]> 00 01 58 
 DMM RAN_conn(IMSI-901700000004620:GERAN-A-0:LU){RAN_CONN_S_AUTH_CIPH}: state_chg to RAN_CONN_S_WAIT_CLASSMARK_UPDATE
 DVLR vlr_lu_fsm(IMSI-901700000004620:GERAN-A-0:LU){VLR_ULA_S_WAIT_AUTH}: state_chg to VLR_ULA_S_WAIT_CIPH
@@ -2988,7 +2988,7 @@
 DVLR vlr_lu_fsm(IMSI-901700000004620:GERAN-A-0:LU){VLR_ULA_S_WAIT_AUTH}: Set Ciphering Mode
 DMM IMSI-901700000004620: to determine whether A5/3 is supported, first ask for a Classmark Update to obtain Classmark 2
 DBSSAP RAN_conn(IMSI-901700000004620:GERAN-A-0:LU){RAN_CONN_S_AUTH_CIPH}: Tx BSSMAP CLASSMARK REQUEST to BSC
-DBSSAP RAN_conn(IMSI-901700000004620:GERAN-A-0:LU){RAN_CONN_S_AUTH_CIPH}: N-DATA.req([])
+DBSSAP RAN_conn(IMSI-901700000004620:GERAN-A-0:LU){RAN_CONN_S_AUTH_CIPH}: N-DATA.req(00 01 58 )
   BSC <--BSSAP-BSS-MANAGEMENT-- MSC: CLASSMARK REQ [L3]> 00 01 58 
 DMM RAN_conn(IMSI-901700000004620:GERAN-A-0:LU){RAN_CONN_S_AUTH_CIPH}: state_chg to RAN_CONN_S_WAIT_CLASSMARK_UPDATE
 DVLR vlr_lu_fsm(IMSI-901700000004620:GERAN-A-0:LU){VLR_ULA_S_WAIT_AUTH}: state_chg to VLR_ULA_S_WAIT_CIPH
@@ -3297,7 +3297,7 @@
 DVLR Process_Access_Request_VLR(IMSI-901700000004620:MSISDN-42342:GERAN-A-0:PAGING_RESP){PR_ARQ_S_WAIT_AUTH}: Set Ciphering Mode
 DMM IMSI-901700000004620:MSISDN-42342: to determine whether A5/3 is supported, first ask for a Classmark Update to obtain Classmark 2
 DBSSAP RAN_conn(IMSI-901700000004620:MSISDN-42342:GERAN-A-0:PAGING_RESP){RAN_CONN_S_AUTH_CIPH}: Tx BSSMAP CLASSMARK REQUEST to BSC
-DBSSAP RAN_conn(IMSI-901700000004620:MSISDN-42342:GERAN-A-0:PAGING_RESP){RAN_CONN_S_AUTH_CIPH}: N-DATA.req([])
+DBSSAP RAN_conn(IMSI-901700000004620:MSISDN-42342:GERAN-A-0:PAGING_RESP){RAN_CONN_S_AUTH_CIPH}: N-DATA.req(00 01 58 )
   BSC <--BSSAP-BSS-MANAGEMENT-- MSC: CLASSMARK REQ [L3]> 00 01 58 
 DMM RAN_conn(IMSI-901700000004620:MSISDN-42342:GERAN-A-0:PAGING_RESP){RAN_CONN_S_AUTH_CIPH}: state_chg to RAN_CONN_S_WAIT_CLASSMARK_UPDATE
 DVLR Process_Access_Request_VLR(IMSI-901700000004620:MSISDN-42342:GERAN-A-0:PAGING_RESP){PR_ARQ_S_WAIT_AUTH}: state_chg to PR_ARQ_S_WAIT_CIPH