[archiso] Add nls_iso8859-1 to initramfs.

Fix FS#40217

Signed-off-by: Gerardo Exequiel Pozzi <vmlinuz386@yahoo.com.ar>

archiso/initcpio/install/archiso_loop_mnt

 #!/bin/bash
 
 build() {
+    add_module "nls_iso8859-1"
     add_runscript
 }