dmaengine: idxd: Fix crash when the event log is disabled

In the Linux kernel, the following vulnerability has been resolved: dmaengine: idxd: Fix crash when the event log is disabled If reporting errors to the event log is not supported by the hardware, and an error that causes Function Level Reset (FLR) is received, the driver will try to restore the event log even if it was not allocated. Also, only try to free the event log if it was properly allocated.