pinctrl: bcm2835: Avoid warning from __irq_do_set_handler

We get a warning during boot with enabled EARLY_PRINTK that
we try to set a irq_chip without data. This is caused by ignoring
the return value of irq_of_parse_and_map(). So avoid calling
gpiochip_set_chained_irqchip() in error case.

Signed-off-by: Stefan Wahren <stefan.wahren@i2se.com>
Fixes: 85ae9e51 ("pinctrl: bcm2835: switch to GPIOLIB_IRQCHIP")
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>