remsim-client: Avoid using 'ci' global variable

Rather, pass it around between functions and attach it to other state.

Also, make it a talloc contxt so other objects can be allocated off it.

Change-Id: I25f592581382238d5640c1f6326dec745f8d1d40
diff --git a/src/client/client.h b/src/client/client.h
index 96a454f..f36e2e3 100644
--- a/src/client/client.h
+++ b/src/client/client.h
@@ -11,6 +11,8 @@
 
 /* main.c */
 
+struct cardem_inst;
+
 struct bankd_client {
 	/* connection to the remsim-server (control) */
 	struct rspro_server_conn srv_conn;
@@ -21,4 +23,6 @@
 	struct app_comp_id peer_comp_id;
 
 	struct bank_slot bankd_slot;
+
+	struct cardem_inst *cardem;
 };