pcu_l1_if_phy: add new PHY API function to initialize PHY

The PHY implementations we currently have do not require any
initialization that has to run directly on startup. This will change
when we introduce support for the E1 based Ericsson RBS CCU. Then we
will have to perform at least one elarly initialization (VTY config
file). So lets add an API function for PHY initialization now.

Related: OS#5198
Change-Id: Ibf2a3a058c826f6ee5b740eee72d5be94d460517
diff --git a/src/pcu_l1_if_phy.h b/src/pcu_l1_if_phy.h
index 318d0aa..297883b 100644
--- a/src/pcu_l1_if_phy.h
+++ b/src/pcu_l1_if_phy.h
@@ -3,6 +3,7 @@
 #include <stdint.h>
 #include <osmocom/core/gsmtap_util.h>
 
+int l1if_init(void);
 void *l1if_open_pdch(uint8_t trx_no, uint32_t hlayer1, struct gsmtap_inst *gsmtap);
 int l1if_connect_pdch(void *obj, uint8_t ts);
 int l1if_pdch_req(void *obj, uint8_t ts, int is_ptcch, uint32_t fn, uint16_t arfcn, uint8_t block_nr, uint8_t *data,