rspro_dec_msg: Simplify msgb ownership handling

Initially it seemed like a good idea that rspro_dec_msg() takes care
of freeing the input msgb when generating a new decoded output
structure.  However, in reality this made the implementation of
every caller more complicated, as it had to treat messages going into
rspro_dec_msg() differently than messages going elsewhere.

Adding to that, not every caller got it right, and the comments were
disagreeing about what happens to msgb ownership in erroneous cases.

Change-Id: I55d5d61922053fd94e2b5a8cdf0d799b29feec98
diff --git a/src/remsim_client.c b/src/remsim_client.c
index e73fcc4..0bfc0a4 100644
--- a/src/remsim_client.c
+++ b/src/remsim_client.c
@@ -90,7 +90,6 @@
 		default:
 			break;
 		}
-		msgb_free(msg);
 		break;
 	case IPAC_PROTO_OSMO:
 		if (!he || msgb_l2len(msg) < sizeof(*he))
@@ -109,6 +108,7 @@
 		goto invalid;
 	}
 
+	msgb_free(msg);
 	return rc;
 
 invalid: