V4L/DVB (12489): pwc - fix few use-after-free and memory leaks

I just happen to peek inside the PWC driver and did not like what I saw
there. Please consider applying the patch below.

Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>
diff --git a/drivers/media/video/pwc/pwc.h b/drivers/media/video/pwc/pwc.h
index 844565b..0902355 100644
--- a/drivers/media/video/pwc/pwc.h
+++ b/drivers/media/video/pwc/pwc.h
@@ -253,6 +253,7 @@
    int snapshot_button_status;		/* set to 1 when the user push the button, reset to 0 when this value is read */
 #ifdef CONFIG_USB_PWC_INPUT_EVDEV
    struct input_dev *button_dev;	/* webcam snapshot button input */
+   char button_phys[64];
 #endif
 
    /*** Misc. data ***/