The deferred_fiq handler used to limit hardware operations to IRQ
unmask only, relying on gpio-omap assigned handler performing the ACKs.
Since commit 80ac93c2 ("gpio: omap: Fix lost edge interrupts") this
is no longer the case as handle_edge_irq() has been replaced with
handle_simmple_irq() which doesn't touch the hardware.

Add single ACK operation per each active IRQ pin to the handler. While
being at it, move unmask operation out of irq_counter loop so it is
also called only once for each active IRQ pin.

Fixes: 80ac93c2 ("gpio: omap: Fix lost edge interrupts")
Signed-off-by: Janusz Krzysztofik <jmkrzyszt@gmail.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>