emulators/virtualbox-ose-legacy: Fix additions build on recent HEAD

Apply same fix used for the main port in commit ef04eff33cf626:

Src HEAD commit 6d3e78ad6c11 vfs_quotactl function signature, adapt
virtualbox code to be able to compile there too.

Reported by: koobs, dim
MFH: 2021Q2

(cherry picked from commit 4792c8e65e73101fef10ed9bb2edb4b4335e6960)