irq: openrisc: perform irqentry in entry code

In preparation for removing HANDLE_DOMAIN_IRQ_IRQENTRY, have
arch/openrisc perform all the irqentry accounting in its entry code. As
arch/openrisc uses GENERIC_IRQ_MULTI_HANDLER, we can use
generic_handle_arch_irq() to do so.

There should be no functional change as a result of this patch.

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Reviewed-by: Marc Zyngier <maz@kernel.org>
Reviewed-by: Stafford Horne <shorne@gmail.com>
Cc: Jonas Bonn <jonas@southpole.se>
Cc: Stefan Kristiansson <stefan.kristiansson@saunalahti.fi>
Cc: Thomas Gleixner <tglx@linutronix.de>