"how do you tell the makinitrd comand to include this file?/"
You have already told mkinitrd to include module aic7xxx. The problem is that imknitrd cannot find the file. You need to compile module aic7xxx into /lib/modules/2.4.22.
I suggest a completely different approach. Distributions like to use initrd because they can compile a lot of modules as m and then load the ones that your configuration needs during boot using initrd. Since you know exactly what your hardware configuration is you can ignore initrd as an unnecessary complication. Instead make every module that you need to access your / partition y in the kernel compile. Also make framebuffers modules y. Then leave initrd out of the bootloader commands for your new kernel.
Be prepared. Create a LifeBoat CD.