[abis_nm] Add abis_nm_bs11_infield_logon to logon as user field

As this user you are able to set the PLL work value which is especially
useful if your BS11 got detuned by an inaccurate oscillator in your E1
card.
diff --git a/openbsc/include/openbsc/abis_nm.h b/openbsc/include/openbsc/abis_nm.h
index 8fe4b0c..9d9b8c1 100644
--- a/openbsc/include/openbsc/abis_nm.h
+++ b/openbsc/include/openbsc/abis_nm.h
@@ -789,6 +789,7 @@
 int abis_nm_bs11_get_trx_power(struct gsm_bts_trx *trx);
 int abis_nm_bs11_logon(struct gsm_bts *bts, u_int8_t level, const char *name, int on);
 int abis_nm_bs11_factory_logon(struct gsm_bts *bts, int on);
+int abis_nm_bs11_infield_logon(struct gsm_bts *bts, int on);
 int abis_nm_bs11_set_trx1_pw(struct gsm_bts *bts, const char *password);
 int abis_nm_bs11_set_pll_locked(struct gsm_bts *bts, int locked);
 int abis_nm_bs11_get_pll_mode(struct gsm_bts *bts);