usb: gadget: f_fs: Fix iterations on endpoints.

When zero endpoints are declared for a function, there is no endpoint
to disable, enable or free, so replace do...while loops with while loops.
Change pre-decrement to post-decrement to iterate the same number of times
when there are endpoints to process.
Signed-off-by: Vincent Pelletier <plr.vincent@gmail.com>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>

drivers/usb/gadget/function/f_fs.c

@@ -1806,7 +1806,7 @@ static void ffs_func_eps_disable(struct ffs_function *func)
 	unsigned long flags;
 
 	spin_lock_irqsave(&func->ffs->eps_lock, flags);
-	do {
+	while (count--) {
 		/* pending requests get nuked */
 		if (likely(ep->ep))
 			usb_ep_disable(ep->ep);
@@ -1817,7 +1817,7 @@ static void ffs_func_eps_disable(struct ffs_function *func)
 			__ffs_epfile_read_buffer_free(epfile);
 			++epfile;
 		}
-	} while (--count);
+	}
 	spin_unlock_irqrestore(&func->ffs->eps_lock, flags);
 }
 
@@ -1831,7 +1831,7 @@ static int ffs_func_eps_enable(struct ffs_function *func)
 	int ret = 0;
 
 	spin_lock_irqsave(&func->ffs->eps_lock, flags);
-	do {
+	while(count--) {
 		struct usb_endpoint_descriptor *ds;
 		int desc_idx;
 
@@ -1867,7 +1867,7 @@ static int ffs_func_eps_enable(struct ffs_function *func)
 
 		++ep;
 		++epfile;
-	} while (--count);
+	}
 	spin_unlock_irqrestore(&func->ffs->eps_lock, flags);
 
 	return ret;
@@ -3448,12 +3448,12 @@ static void ffs_func_unbind(struct usb_configuration *c,
 
 	/* cleanup after autoconfig */
 	spin_lock_irqsave(&func->ffs->eps_lock, flags);
-	do {
+	while (count--) {
 		if (ep->ep && ep->req)
 			usb_ep_free_request(ep->ep, ep->req);
 		ep->req = NULL;
 		++ep;
-	} while (--count);
+	}
 	spin_unlock_irqrestore(&func->ffs->eps_lock, flags);
 	kfree(func->eps);
 	func->eps = NULL;