[BUGFIX] Allow to upload online media via file list

It was not possible due to a form name mixup to add online media files
via the FileList in TYPO3 v9 anymore.

Related: #82436
Related: #81763
Resolves: #83151
Releases: master
Change-Id: Ica0ed049f685bf20b98f0a599adf61ec3874017a
Reviewed-on: https://review.typo3.org/54847


Reviewed-by: Andreas Fernandez <typo3@scripting-base.de>
Tested-by: Andreas Fernandez <typo3@scripting-base.de>
Tested-by: TYPO3com <no-reply@typo3.com>
Reviewed-by: Susanne Moog <susanne.moog@typo3.org>
Tested-by: Susanne Moog <susanne.moog@typo3.org>