Same logic as your code, but once the split operation has been completed, the volume will no longer show up in the output of the "Get-NcVolClone" command (since it is no longer a clone). In your code, you could test for its absence from the output of that command and then branch from there based on that data.
$SplitStatus = Get-NcVolClone -Volume volume01
while ($SplitStatus){
Write-Host "Split in progress..."
Start-Sleep 30
$SplitStatus = Get-NcVolClone -Volume volume01
}