DevAPI: Allow using device_proc_by_id with const struct cgpu_info

deviceapi.c

@@ -1088,9 +1088,9 @@ void close_device_fd(struct thr_info * const thr)
 }
 
 
-struct cgpu_info *device_proc_by_id(struct cgpu_info * const dev, const int procid)
+struct cgpu_info *device_proc_by_id(const struct cgpu_info * const dev, const int procid)
 {
-	struct cgpu_info *proc = dev;
+	struct cgpu_info *proc = (void*)dev;
 	for (int i = 0; i < procid; ++i)
 	{
 		proc = proc->next_proc;

deviceapi.h

@@ -114,6 +114,6 @@ extern void close_device_fd(struct thr_info *);
 	for (struct cgpu_info *procvar = dev; procvar; procvar = procvar->next_proc)
 #define for_each_logical_proc(procvar, dev)  \
 	for (struct cgpu_info *procvar = dev; procvar && procvar->device == (dev); procvar = procvar->next_proc)
-extern struct cgpu_info *device_proc_by_id(struct cgpu_info *dev, int procid);
+extern struct cgpu_info *device_proc_by_id(const struct cgpu_info *dev, int procid);
 
 #endif