Originally OMAP MPUIO GPIO irqchip was implemented using Generic irq
chip, but after set of reworks Generic irq chip code was replaced by
common OMAP GPIO implementation and finally removed by
commit d2d05c65c40e ("gpio: omap: Fix regression for MPUIO interrupts").
Unfortunately, above commit left .irq_mask/unmask callbacks assigned
as below for MPUIO GPIO case:
irqc->irq_mask = irq_gc_mask_set_bit;
irqc->irq_unmask = irq_gc_mask_clr_bit;
This now causes boot failure on OMAP1 platforms, after
commit 450fa54cfd66 ("gpio: omap: convert to use generic irq handler")
which forces these callbacks to be called during GPIO IRQs mapping
from gpiochip_irq_map:
Hence, fix it by remove obsolete callbacks assignment. After this
change omap_gpio_mask_irq()/omap_gpio_unmask_irq() will be used
for MPUIO IRQs masking, but this now happens anyway from
omap_gpio_irq_startup/shutdown().