drivers/video/backlight/lp855x_bl.c: fix compiler warning in lp855x_probe

While doing with make W=1 gcc (gcc (GCC) 4.7.2 20121109 (Red Hat
4.7.2-8)) I found

  drivers/video/backlight/lp855x_bl.c: In function `lp855x_probe':
  drivers/video/backlight/lp855x_bl.c:342:35: warning: variable `mode' set but not used [-Wunused-but-set-variable]

fixed by removing it as since its not used anywhere

Signed-off-by: Devendra Naga <devendra.aaru@gmail.com>
Acked-by: Milo Kim <milo.kim@ti.com>
Cc: Jingoo Han <jg1.han@samsung.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>