Informações tiradas de aqui .
You need to recompile the kernel, if you compile with built-in support then you're safe, but mkinitrd will only take the modules that are needed to boot the running kernel - meaning that unless you can boot the machine into Fedora with AHCI on and then run mkinitrd, it won't take it by default.
You can use the --preload option to manually specific modules though, so you could always try turning AHCI off, booting Fedora, making your custom image:
mkinitrd --allow-missing --preload=ahci --force-scsi-probe /boot/initrd-'uname -r'-custom 'uname -r'
Then reboot, enable AHCI and during the GRUB bootup menu edit the "initrd" line to load the custom image you just created. When that's done, reinstall the latest kernel (or yum update one) to create a good initrd.