[BUGFIX] TCA: subtypes_addlist not processed

TCA: subtypes_addlist is not processed
if the subtype_value_field is in a palette

Change-Id: I6bcaaf36c330962c1d7d9fdd4a73ae502e9710dc
Fixes: #30636
Releases: 4.5, 4.7, 6.0, 6.1
Reviewed-on: https://review.typo3.org/19652
Reviewed-by: Philipp Gampe
Tested-by: Philipp Gampe
Reviewed-by: Stefan Neufeind
Tested-by: Stefan Neufeind