HID: picolcd: Prevent NULL pointer dereference on _remove()

When picolcd is switched into bootloader mode (for FW flashing) make
sure not to try to dereference NULL-pointers of feature-devices during
unplug/unbind.

This fixes following BUG:
BUG: unable to handle kernel NULL pointer dereference at 00000298
IP: [<f811f56b>] picolcd_exit_framebuffer+0x1b/0x80 [hid_picolcd]
*pde = 00000000
Oops: 0000 [#1]
Modules linked in: hid_picolcd syscopyarea sysfillrect sysimgblt fb_sys_fops
CPU: 0 PID: 15 Comm: khubd Not tainted 3.11.0-rc7-00002-g50d62d4 #2
EIP: 0060:[<f811f56b>] EFLAGS: 00010292 CPU: 0
EIP is at picolcd_exit_framebuffer+0x1b/0x80 [hid_picolcd]
Call Trace:
[<f811d1ab>] picolcd_remove+0xcb/0x120 [hid_picolcd]
[<c1469b09>] hid_device_remove+0x59/0xc0
[<c13464ca>] __device_release_driver+0x5a/0xb0
[<c134653f>] device_release_driver+0x1f/0x30
[<c134603d>] bus_remove_device+0x9d/0xd0
[<c13439a5>] device_del+0xd5/0x150
[<c14696a4>] hid_destroy_device+0x24/0x60
[<c1474cbb>] usbhid_disconnect+0x1b/0x40
...

Signed-off-by: Bruno Prémont <[e-mail]>
Cc: [e-mail]
Signed-off-by: Jiri Kosina <[e-mail]>

drivers/hid/hid-picolcd_cir.c

···
 	struct rc_dev *rdev = data->rc_dev;
 
 	data->rc_dev = NULL;
-	rc_unregister_device(rdev);
+	if (rdev)
+		rc_unregister_device(rdev);
 }
 

drivers/hid/hid-picolcd_fb.c

···
 void picolcd_exit_framebuffer(struct picolcd_data *data)
 {
 	struct fb_info *info = data->fb_info;
-	struct picolcd_fb_data *fbdata = info->par;
+	struct picolcd_fb_data *fbdata;
 	unsigned long flags;
 
+	if (!info)
+		return;
+
 	device_remove_file(&data->hdev->dev, &dev_attr_fb_update_rate);
+	fbdata = info->par;
 
 	/* disconnect framebuffer from HID dev */
 	spin_lock_irqsave(&fbdata->lock, flags);