CONFIG_OLD_IRQ_AT91 is not available for thedefaultarchitecture x86.
Result is shown for architecture arm

CONFIG_OLD_IRQ_AT91 (not configurable)

modulename: irq.ko

configname: CONFIG_OLD_IRQ_AT91

Linux Kernel Configuration
└─>OLD_IRQ_AT91
In linux kernel since version 3.18 (release Date: 2014-12-07)  
source code:
arch/arm/mach-at91/irq.c
selects
CONFIG_MULTI_IRQ_HANDLER
CONFIG_SPARSE_IRQ


is depended by
CONFIG_ARCH_AT91X40