mboxd: Refactor and rename mbox.h to mboxd.h

Refine the purpose of the header file to represent what's required for
the daemon itself, not its constituent pieces. Rather, split those
definitions out to their respective header files and include them as
necessary.

Finally the header file is renamed to better reflect its purpose.

Change-Id: I48c409f57d96c844589cd865b24f197477dfe87c
Signed-off-by: Andrew Jeffery <andrew@aj.id.au>
diff --git a/control_dbus.h b/control_dbus.h
index 4a3b2ff..17e4dec 100644
--- a/control_dbus.h
+++ b/control_dbus.h
@@ -1,7 +1,7 @@
 #ifndef DBUS_CONTROL_H
 #define DBUS_CONTROL_H
 
-#include "mbox.h"
+struct mbox_context;
 
 int control_dbus_init(struct mbox_context *context);
 void control_dbus_free(struct mbox_context *context);