refactor(iso): Rely on select_part for EFI partition identification (#1)

setup.sh

@@ -210,12 +210,9 @@ function mount_system () {
     zfs mount "${zpool_name}"'/root/'"${zfs_arch_dataset_name}"
     zfs mount -a
 
-    declare efi_part
-    efi_part="$(get_parts 'efi')"
-    if we_have_exactly_one_part 'efi' "${efi_part}"; then
+    local efi_part="$(select_part 'efi')"
     mkdir -p '/mnt/efi'
     mount "${efi_part}" '/mnt/efi'
-    fi
 }
 
 function copy_zpool_cache () {