[BUGFIX] Drop usage of iconFile if typeicon_classes is used in TCA

If typeicon_classes is used, the iconFile is not required.

Furthermore using an icon identifier instead of a file in iconFile
triggers an entry in the deprecation log and a wrong TCA migration.

The identifiers are not used anywhere else and can be removed in the
IconRegistry.

Change-Id: Ib6df3566e9b23d59cab730cc1246affe84891929
Resolves: #70678
Releases: master
Reviewed-on: http://review.typo3.org/44042


Reviewed-by: Frank Nägler <frank.naegler@typo3.org>
Tested-by: Frank Nägler <frank.naegler@typo3.org>
Reviewed-by: Anja Leichsenring <aleichsenring@ab-softlab.de>
Tested-by: Anja Leichsenring <aleichsenring@ab-softlab.de>