genirq: replace irq_gc_ack() with {set,clr}_bit variants (fwd)

This fixes a regression introduced by e59347a "arm: orion:
Use generic irq chip".

Depending on the device, interrupts acknowledgement is done by setting
or by clearing a dedicated register. Replace irq_gc_ack() with some
{set,clr}_bit variants allows to handle both cases.

Note that this patch affects the following SoCs: Davinci, Samsung and
Orion. Except for this last, the change is minor: irq_gc_ack() is just
renamed into irq_gc_ack_set_bit().

For the Orion SoCs, the edge GPIO interrupts support is currently
broken. irq_gc_ack() try to acknowledge a such interrupt by setting
the corresponding cause register bit. The Orion GPIO device expect the
opposite. To fix this issue, the irq_gc_ack_clr_bit() variant is used.

Tested on Network Space v2.

Reported-by: Joey Oravec <joravec@drewtech.com>
Signed-off-by: Simon Guinot <sguinot@lacie.com>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
diff --git a/arch/arm/plat-orion/gpio.c b/arch/arm/plat-orion/gpio.c
index 5b4fffa..41ab97e 100644
--- a/arch/arm/plat-orion/gpio.c
+++ b/arch/arm/plat-orion/gpio.c
@@ -432,7 +432,7 @@
 	ct->regs.mask = ochip->mask_offset + GPIO_EDGE_MASK_OFF;
 	ct->regs.ack = GPIO_EDGE_CAUSE_OFF;
 	ct->type = IRQ_TYPE_EDGE_RISING | IRQ_TYPE_EDGE_FALLING;
-	ct->chip.irq_ack = irq_gc_ack;
+	ct->chip.irq_ack = irq_gc_ack_clr_bit;
 	ct->chip.irq_mask = irq_gc_mask_clr_bit;
 	ct->chip.irq_unmask = irq_gc_mask_set_bit;
 	ct->chip.irq_set_type = gpio_irq_set_type;