pinctrl: bcm2835: Remove gpiochip on error

A failure in gpiochip_irqchip_add leads to a leak of a gpiochip. Fix
the leak with the use of devm_gpiochip_add_data.

Fixes: 85ae9e51 ("pinctrl: bcm2835: switch to GPIOLIB_IRQCHIP")
Signed-off-by: Phil Elwell <phil@raspberrypi.org>