I added the module to /lib/mkinitrd/scripts/boot-usb.sh and it has remained for me. I have upgraded the kernel twice and have run mkinitrd -v several times manually since the edit, and mkinitrd still includes ohci_pci during build. The file has not changed since the edit. I removed the modules that I had added to /etc/sysconfig/kernel
I added the module to /lib/mkinitrd/ scripts/ boot-usb. sh and it has remained for me. I have upgraded the kernel twice and have run mkinitrd -v several times manually since the edit, and mkinitrd still includes ohci_pci during build. The file has not changed since the edit. I removed the modules that I had added to /etc/sysconfig/ kernel