Mark deprecated function as such

Mark abis_nm_debugp_foh() function superseded by macro with the same
name as deprecated.

Change-Id: I2d3ea2b56aff6b687f72f832360b8cb8a24164e9
diff --git a/src/gsm/abis_nm.c b/src/gsm/abis_nm.c
index 73e3c7e..9839d29 100644
--- a/src/gsm/abis_nm.c
+++ b/src/gsm/abis_nm.c
@@ -597,6 +597,7 @@
 
 /* this is just for compatibility reasons, it is now a macro */
 #undef abis_nm_debugp_foh
+OSMO_DEPRECATED("Use abis_nm_debugp_foh macro instead")
 void abis_nm_debugp_foh(int ss, struct abis_om_fom_hdr *foh)
 {
 	DEBUGP(ss, "OC=%s(%02x) INST=(%02x,%02x,%02x) ",