lc15/oc2g: fix function signature of l1if_open_pdch()

The function signatures l1if_open_pdch() in the code for lc15 and oc2g
differ from what is defined in pcu_l1_if_phy.h. Lets update the
signatures so that they match the prototype.

Related: OS#5198
Change-Id: If1693b1b74c1808596d7da639b860f7b226385c0
diff --git a/src/osmo-bts-oc2g/oc2g_l1_if.c b/src/osmo-bts-oc2g/oc2g_l1_if.c
index a41e7af..dae5908 100644
--- a/src/osmo-bts-oc2g/oc2g_l1_if.c
+++ b/src/osmo-bts-oc2g/oc2g_l1_if.c
@@ -366,7 +366,7 @@
 	return 0;
 }
 
-void *l1if_open_pdch(uint8_t trx_no, uint32_t hlayer1)
+void *l1if_open_pdch(uint8_t trx_no, uint32_t hlayer1, struct gsmtap_inst *gsmtap)
 {
 	struct oc2gl1_hdl *fl1h;
 	int rc;