[BUGFIX] Check folder access for inline uploader

Before the inline drag and drop upload functionality to the default
upload folder is enabled it is made sure that the upload folder
is initialized and that the user is allowed to add files.

Resolves: #55628
Releases: 6.2
Change-Id: Ia18678dc432c6f0addea33aa0389db54297435e3
Reviewed-on: https://review.typo3.org/27302
Reviewed-by: Lorenz Ulrich
Tested-by: Lorenz Ulrich
Reviewed-by: Wouter Wolters
Reviewed-by: Markus Klein
Tested-by: Markus Klein