leds: leds-gpio: Convert gpio_blink_set() to use GPIO descriptors

Commit 21f2aae91e902aad ("leds: leds-gpio: Add support for GPIO
descriptors") already converted most of the driver to use GPIO descriptors.
What is still missing is the platform specific hook gpio_blink_set() and
board files which pass legacy GPIO numbers to this driver in platform data.

In this patch we handle the former and convert gpio_blink_set() to take
GPIO descriptor instead. In order to do this we convert the existing four
users to accept GPIO descriptor and translate it to legacy GPIO number in
the platform code. This effectively "pushes" legacy GPIO number usage from
the driver to platforms.

Also add comment to the remaining block describing that it is legacy code
path and we are getting rid of it eventually.

Suggested-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Acked-by: Andrew Lunn <andrew@lunn.ch>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Acked-by: Alexandre Courbot <acourbot@nvidia.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>