[BUGFIX] Correct TCA inclusion for uploads rendering

In the method that renders the uploads in css_styled_content
the call to load the TCA was replaced with its Frontend
counterpart to enable access to the configuration of custom
fields in tt_content.

Fixes: #44145
Branches: 4.5, 4.6, 4.7, 6.0, 6.1

Change-Id: I26f67fcfbf11db25c80ebe93ddd1e81167d828a9
Reviewed-on: https://review.typo3.org/17716
Reviewed-by: Georg Ringer
Tested-by: Georg Ringer
Reviewed-on: https://review.typo3.org/17717
Reviewed-on: https://review.typo3.org/17718