drm/pl111: Fix unused variable warning

drm/pl111: Fix unused variable warning

drivers/gpu/drm/pl111/pl111_display.c: In function ‘pl111_display_init’:
drivers/gpu/drm/pl111/pl111_display.c:551:17: warning: unused variable
‘dev’ [-Wunused-variable]
  struct device *dev = drm->dev;
                 ^
Fixes: 704ec924c1cb ("drm/pl111: Drop special pads config check")
Cc: Linus Walleij <linus.walleij@linaro.org>
Cc: Eric Anholt <eric@anholt.net>
Cc: David Airlie <airlied@linux.ie>
Cc: Daniel Vetter <daniel@ffwll.ch>
Signed-off-by: Shaokun Zhang <zhangshaokun@hisilicon.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/1564996456-55677-1-git-send-email-zhangshaokun@hisilicon.com