sh: ecovec24: don't set unused fields in platform data

Platform data fields other than fbdev are no longer used by the
backlight driver. Remove them.

Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Tested-by: Jacopo Mondi <jacopo+renesas@jmondi.org>
Signed-off-by: Lee Jones <lee.jones@linaro.org>