powerpc/powernv/vas: Fix order of cleanup in vas_window_init_dbgdir()

Fix the order of cleanup to ensure we free the name buffer in case
of an error creating 'hvwc' or 'info' files.

Signed-off-by: Sukadev Bhattiprolu <sukadev@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>