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/osmo-bts-sysmo/sysmo_l1_if.c b/src/osmo-bts-sysmo/sysmo_l1_if.c
index 18378b6..348497f 100644
--- a/src/osmo-bts-sysmo/sysmo_l1_if.c
+++ b/src/osmo-bts-sysmo/sysmo_l1_if.c
@@ -386,3 +386,8 @@
 	talloc_free(fl1h);
 	return 0;
 }
+
+int l1if_init(void)
+{
+	return 0;
+}