Revert "EFI Filesystem must be Fat32 formatted"

Using fat32 causes failed boots on e.g AWS EC2 arm.
This must be solved differently with an attribute
to configure it.

This reverts commit b8641bd.

kiwi/builder/disk.py

@@ -806,11 +806,11 @@ def _build_boot_filesystems(
         system_efi = None
         if 'efi' in device_map:
             log.info(
-                'Creating EFI(fat32) filesystem on %s',
+                'Creating EFI(fat16) filesystem on %s',
                 device_map['efi'].get_device()
             )
             filesystem = FileSystem.new(
-                'fat32', device_map['efi'], self.root_dir + '/boot/efi/'
+                'fat16', device_map['efi'], self.root_dir + '/boot/efi/'
             )
             filesystem.create_on_device(
                 label=self.disk_setup.get_efi_label()