When gpio core dynamically allocate gpio number for a port, it starts
from the end of the total range, 0 ~ ARCH_NR_GPIOS.  That said, the
earlier a port gets probed, the bigger gpio number it gets assigned.
To match this, the irq_base for gpio should be assigned from
'MXC_GPIO_IRQ_START + ARCH_NR_GPIOS' decreasingly.

Signed-off-by: Shawn Guo <shawn.guo@linaro.org>

The of_irq_init() expects the callback passed by .data of of_device_id
return 'int' instead of 'void'.  This patch fixes it to have
irq_init_cb() return the correct value, and in turn have the secondary
interrupt controller (gpio in this case) initialized properly and also
eliminate the error message 'of_irq_init: children remain, but no
parents' which was overlooked before.

Signed-off-by: Shawn Guo <shawn.guo@linaro.org>

It adds generic device tree based machine support for imx6q.

Signed-off-by: Shawn Guo <shawn.guo@linaro.org>