[media] v4l2-flash-led-class: remove a now unused var

commit 079933db ("[media] v4l: flash led class: Fix of_node release
in probe() error path") removed the need of an ancillary var at
the release function, as reported by smatch:

drivers/media/v4l2-core/v4l2-flash-led-class.c: In function 'v4l2_flash_release':
drivers/media/v4l2-core/v4l2-flash-led-class.c:678:23: warning: variable 'led_cdev' set but not used [-Wunused-but-set-variable]
  struct led_classdev *led_cdev;
                       ^~~~~~~~

Get rid of it.

Fixes: commit 079933db ("[media] v4l: flash led class: Fix of_node release in probe() error path")
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>