tm6000: drop unnecessary list_empty

list_for_each_entry is able to handle an empty list.
The only effect of avoiding the loop is not initializing the
index variable.
Drop list_empty tests in cases where these variables are not
used.

Note that list_for_each_entry is defined in terms of list_first_entry,
which indicates that it should not be used on an empty list.  But in
list_for_each_entry, the element obtained by list_first_entry is not
really accessed, only the address of its list_head field is compared
to the address of the list head, so the list_first_entry is safe.

The semantic patch that makes this change is as follows:
(http://coccinelle.lip6.fr/)

<smpl>
@@
expression x,e;
iterator name list_for_each_entry;
statement S;
identifier i;
@@

-if (!(list_empty(x))) {
   list_for_each_entry(i,x,...) S
- }
 ... when != i
? i = e
</smpl>
Signed-off-by: Julia Lawall <Julia.Lawall@inria.fr>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>

drivers/media/usb/tm6000/tm6000-core.c

@@ -853,12 +853,10 @@ int tm6000_call_fillbuf(struct tm6000_core *dev, enum tm6000_ops_type type,
 
 	/* FIXME: tm6000_extension_devlist_lock should be a spinlock */
 
-	if (!list_empty(&tm6000_extension_devlist)) {
 	list_for_each_entry(ops, &tm6000_extension_devlist, next) {
 		if (ops->fillbuf && ops->type == type)
 			ops->fillbuf(dev, buf, size);
 	}
-	}
 
 	return 0;
 }
@@ -898,12 +896,10 @@ void tm6000_init_extension(struct tm6000_core *dev)
 	struct tm6000_ops *ops = NULL;
 
 	mutex_lock(&tm6000_devlist_mutex);
-	if (!list_empty(&tm6000_extension_devlist)) {
 	list_for_each_entry(ops, &tm6000_extension_devlist, next) {
 		if (ops->init)
 			ops->init(dev);
 	}
-	}
 	mutex_unlock(&tm6000_devlist_mutex);
 }
 
@@ -912,11 +908,9 @@ void tm6000_close_extension(struct tm6000_core *dev)
 	struct tm6000_ops *ops = NULL;
 
 	mutex_lock(&tm6000_devlist_mutex);
-	if (!list_empty(&tm6000_extension_devlist)) {
 	list_for_each_entry(ops, &tm6000_extension_devlist, next) {
 		if (ops->fini)
 			ops->fini(dev);
 	}
-	}
 	mutex_unlock(&tm6000_devlist_mutex);
 }