[BUGFIX] Re-Introduce feature to go one level up in file list

When the file list has been reworked to use FAL instead of
plain PHP file functions the feature to go one level up has
been removed accidentilly. This patch reintroduces the
original behaviour known from TYPO3 CMS 4.x.

Releases: 6.2
Resolves: #51866
Change-Id: Iad334c90d575f2b2f3b47af71e23c721edd76e1e
Reviewed-on: https://review.typo3.org/25812
Reviewed-by: Xavier Perseguers
Tested-by: Xavier Perseguers
Reviewed-by: Steffen Müller
Tested-by: Steffen Müller