power: supply: bq24735: Drop unused include

The driver include <linux/gpio.h> but actually only use
<linux/gpio/consumer.h> which is includes below. Drop the
surplus legacy header include.

Cc: Peter Rosin <peda@axentia.se>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>