net: enetc: distinguish error from valid pointers in enetc_fixup_clear_rss_rfs()

enetc_psi_create() returns an ERR_PTR() or a valid station interface
pointer, but checking for the non-NULL quality of the return code blurs
that difference away. So if enetc_psi_create() fails, we call
enetc_psi_destroy() when we shouldn't. This will likely result in
crashes, since enetc_psi_create() cleans up everything after itself when
it returns an ERR_PTR().

Fixes: f016804 ("net: enetc: reimplement RFS/RSS memory clearing as PCI quirk")
Reported-by: Dan Carpenter <dan.carpenter@linaro.org>
Closes: https://lore.kernel.org/netdev/582183ef-e03b-402b-8e2d-6d9bb3c83bd9@moroto.mountain/
Suggested-by: Dan Carpenter <dan.carpenter@linaro.org>
Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Link: https://lore.kernel.org/r/20230906141609.247579-1-vladimir.oltean@nxp.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Author: vladimiroltean

drivers/net/ethernet/freescale/enetc/enetc_pf.c

@@ -1402,7 +1402,7 @@ static void enetc_fixup_clear_rss_rfs(struct pci_dev *pdev)
 		return;
 
 	si = enetc_psi_create(pdev);
-	if (si)
+	if (!IS_ERR(si))
 		enetc_psi_destroy(pdev);
 }
 DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_FREESCALE, ENETC_DEV_ID_PF,