pcu_l1_if_phy: fix API function names

The functions l1if_open_pdch and l1if_close_pdch have a misleading
naming since what they actually do is opening and closing the TRX since
they return and accept a context (obj) that is valid for a whole TRX.
This also explains why the other functions accept a timeslot as
parameter in addition to the context. Let's rename those functions so
that it is clear what they do.

Related: OS#6022
Change-Id: I395a60b2fba39bac4facec78989bac20f0cef0d3
diff --git a/src/osmo-bts-oc2g/oc2g_l1_if.c b/src/osmo-bts-oc2g/oc2g_l1_if.c
index 93b4654..2c9da72 100644
--- a/src/osmo-bts-oc2g/oc2g_l1_if.c
+++ b/src/osmo-bts-oc2g/oc2g_l1_if.c
@@ -372,7 +372,7 @@
 	return 0;
 }
 
-void *l1if_open_pdch(uint8_t bts_nr, uint8_t trx_no, uint32_t hlayer1, struct gsmtap_inst *gsmtap)
+void *l1if_open_trx(uint8_t bts_nr, uint8_t trx_no, uint32_t hlayer1, struct gsmtap_inst *gsmtap)
 {
 	struct oc2gl1_hdl *fl1h;
 	int rc;
@@ -401,7 +401,7 @@
 	return fl1h;
 }
 
-int l1if_close_pdch(void *obj)
+int l1if_close_trx(void *obj)
 {
 	struct oc2gl1_hdl *fl1h = obj;
 	if (fl1h)