pcu_l1_if: get rid of strange paging group calculation

The PCU uses a 16 bit integer value as paging group which does in fact
not really resamble the paging group. Instead it encodes the last three
digits of the IMSI from which the paging group can be calculated. The
value is then eventually converted back to Ascii-digits and then sent
over the PCU-IF interface. Lets get rid of this weird conversion and
use the IMSI directly.

Change-Id: I40d7fc14c9591b3de091e425faaf325421c70a0e
diff --git a/src/pcu_l1_if.h b/src/pcu_l1_if.h
index d3d70e4..3865402 100644
--- a/src/pcu_l1_if.h
+++ b/src/pcu_l1_if.h
@@ -148,7 +148,7 @@
 		       uint8_t *data, size_t data_len);
 void pcu_l1if_tx_agch(struct gprs_rlcmac_bts *bts, bitvec *block, int len);
 
-void pcu_l1if_tx_pch(struct gprs_rlcmac_bts *bts, bitvec *block, int plen, uint16_t pgroup);
+void pcu_l1if_tx_pch(struct gprs_rlcmac_bts *bts, bitvec *block, int plen, const char *imsi);
 void pcu_l1if_tx_pch_dt(struct gprs_rlcmac_bts *bts, bitvec *block, int plen, const char *imsi, uint32_t tlli);
 #endif
 
@@ -176,7 +176,6 @@
 	uint8_t len, uint32_t fn, struct pcu_l1_meas *meas);
 
 void pcu_rx_block_time(struct gprs_rlcmac_bts *bts, uint16_t arfcn, uint32_t fn, uint8_t ts_no);
-uint16_t imsi2paging_group(const char* imsi);
 
 struct e1_conn_pars {
 	/* Number of E1 line */