ARM: SAMSUNG: remove GPIO flags in dev-backlight

ARM: SAMSUNG: remove GPIO flags in dev-backlight

The pwm-backlight driver is moving to use the gpiod interface,
which has its own mapping mechanism for platform data GPIOs.
These mappings carry GPIO properties like active low so they don't have
to be explicitly handled by GPIO consumers.

Because of this change, the enable_gpio_flags member of
platform_pwm_backlight_data is going away. dev-backlight was passing
this member, but had no user making use of it, so it can safely be
removed. Further GPIOs used by pwm-backlight are expected to be
defined using the mechanisms provided by the gpiod API.

Signed-off-by: Alexandre Courbot <acourbot@nvidia.com>
Reviewed-by: Jingoo Han <jg1.han@samsung.com>
Acked-by: Kukjin Kim <kgene.kim@samsung.com>
Signed-off-by: Thierry Reding <thierry.reding@gmail.com>