[BUGFIX] Increase length of identifier field in sys_file

Sometimes the identifier is longer than 200 chars. This patch increases
the maximum length to 512 characters.

Resolves: #48912
Releases: 6.2, 6.1, 6.0
Change-Id: I67edc1facf972d2ffef09a3204edc556464afda5
Reviewed-on: https://review.typo3.org/23938
Reviewed-by: Christian Kuhn
Tested-by: Christian Kuhn