pinctrl: at91: Fix error handling while doing gpiochio_irqchip_add

This patch removes a call to panic function when gpiochio_irqchip_add
fails and just returns the error to the calling function.
Same return value is used to handle the error case and adds a lable
to release resources on error.
The error message has been improved to indicate failure to add irqchip
to gpiochip.

This also changes first argument to function at91_gpio_of_irq_setup from
struct device_node to struct platform_device. Because The device_node
argument was anyway not being used. Passed pdev so that on failure dev_err
can use &pdev->dev and log can be associated with proper device.

CC: Jean-Christophe Plagniol-Villard <plagnioj@jcrosoft.com>
CC: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Pramod Gurav <pramod.gurav@smartplayin.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>