Fix booting test VMs on some hardware

Systems without any AHCI devices will result in an initramfs generated
by mkinitcpio without any AHCI kernel drivers. Drives attached to the
test VM are connected via AHCI, so they will not show up. Explicitly
requiring the kernel module resolves this issue.

testing/setup.sh

@@ -171,9 +171,9 @@ EOF
   mkdir -p "${MKINITCPIOD}"
 
   cat << EOF > "${MKINITCPIOD}/base.conf"
-MODULES=()
+MODULES=(ahci.ko)
 BINARIES=()
-FILEs=()
+FILES=()
 HOOKS=(base udev autodetect modconf block filesystems keyboard)
 COMPRESSION="cat"
 EOF