remsim-client: move from common 'src' directory to 'src/client'

As both the bankd and the server already are in src/bankd and
src/server, respectively: Let's unify this and have the client
also in its own sub-directory.

Change-Id: I67a3a5941434f09f7099c2cdb19c126cea305a73
diff --git a/src/rspro_client_fsm.h b/src/rspro_client_fsm.h
index ca59c77..2f3f7fc 100644
--- a/src/rspro_client_fsm.h
+++ b/src/rspro_client_fsm.h
@@ -4,6 +4,8 @@
 #include <osmocom/abis/ipa.h>
 #include <osmocom/rspro/RsproPDU.h>
 
+#include "rspro_util.h"
+
 enum server_conn_fsm_event {
 	SRVC_E_ESTABLISH,	/* instruct SRVC to (re)etablish TCP connection to bankd */
 	SRVC_E_TCP_UP,