HID: fix lock imbalance in hidraw

Add omitted unlock_kernel() to hidraw_ioctl().
Added in 979c407e3b
(HID: Push down BKL into ioctl handler in hidraw).

Corresponing sparse warning:
drivers/hid/hidraw.c:267:9: warning: context imbalance in 'hidraw_ioctl': wrong count at exit
drivers/hid/hidraw.c:267:9:    context 'kernel_lock': wanted 0, got 1

Signed-off-by: Jiri Slaby <jirislaby@gmail.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>

drivers/hid/hidraw.c

@@ -264,6 +264,7 @@ static long hidraw_ioctl(struct file *file, unsigned int cmd,
 		default:
 			ret = -ENOTTY;
 	}
+	unlock_kernel();
 	return ret;
 }