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

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.

Fixes: 6078a315aec1 ("dmaengine: idxd: Add idxd_device_config_save() and idxd_device_config_restore() helpers")
Reviewed-by: Dave Jiang <dave.jiang@intel.com>
Signed-off-by: Vinicius Costa Gomes <vinicius.gomes@intel.com>
Link: https://patch.msgid.link/20260121-idxd-fix-flr-on-kernel-queues-v3-v3-2-7ed70658a9d1@intel.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>