rtc: rtc-v3020: use gpio_request_array()

Using gpio_request_array()/gpio_free_array() can make the code
simpler because it can set the direction and initial value
in one shot and the for loop is unnecessary.

Also, struct v3020_gpio is removed, because the struct v3020_gpio
is replaced with struct gpio.

Signed-off-by: Jingoo Han <jg1.han@samsung.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>