USB: host: sl811: remove dentry pointer for debugfs

There is no need to keep the dentry pointer around for the created
debugfs file, as it is only needed when removing it from the system.
When it is to be removed, ask debugfs itself for the pointer, to save on
storage and make things a bit simpler.

Cc: [e-mail]
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

drivers/usb/host/sl811-hcd.c

···
 /* expect just one sl811 per system */
 static void create_debug_file(struct sl811 *sl811)
 {
-	sl811->debug_file = debugfs_create_file("sl811h", S_IRUGO,
-						usb_debug_root, sl811,
-						&sl811h_debug_fops);
+	debugfs_create_file("sl811h", S_IRUGO, usb_debug_root, sl811,
+			    &sl811h_debug_fops);
 }
 
 static void remove_debug_file(struct sl811 *sl811)
 {
-	debugfs_remove(sl811->debug_file);
+	debugfs_remove(debugfs_lookup("sl811h", usb_debug_root));
 }
 
 /*-------------------------------------------------------------------------*/

drivers/usb/host/sl811.h

···
 	void __iomem		*addr_reg;
 	void __iomem		*data_reg;
 	struct sl811_platform_data	*board;
-	struct dentry 		*debug_file;
 
 	unsigned long		stat_insrmv;
 	unsigned long		stat_wake;