[BUGFIX] DocumentEditController save broken

With changing the input type=image to input type=submit, the x/y
values are no longer transferred the EditDocumentController
checked for, and content is no longer saved.
Adapt the controller code for the new parameters.

Resolves: #68776
Releases: master
Change-Id: Id1f3ec59ec728b48583c8ef79020c2feede4fd54
Reviewed-on: http://review.typo3.org/42297


Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>
Reviewed-by: Benni Mack <benni@typo3.org>
Tested-by: Benni Mack <benni@typo3.org>