genirq/irqdesc: Drop excess kernel-doc entry @lookup

Fix kernel-doc warning in irqdesc.c:

../kernel/irq/irqdesc.c:692: warning: Excess function parameter 'lookup' description in 'handle_domain_irq'

Fixes: e1c05491 ("genirq: Move non-irqdomain handle_domain_irq() handling into ARM's handle_IRQ()")
Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20210628004044.9011-1-rdunlap@infradead.org