core/pcie-slots: Fix coverity possible NULL dereference
core/pcie-slots: Fix coverity possible NULL dereference

Coverity has found a senario where there could be a NULL dereference,
it is likely that in practice we wouldn't hit this. Coverity does point
out that all other callers of pcie_slot_create() do check for the NULL
return, as such it makes sense to add a check.

Fixes: CID 173756
Signed-off-by: Cyril Bur <6ce38dade8c4b52fd55c193fae70fd1d1275c3c3@au1.ibm.com>
Signed-off-by: Stewart Smith <ec31ab75ddf977353c8f660f92ea8b23f64aef25@linux.vnet.ibm.com>

open-power/skiboot,open-power/skiboot,shenki/skiboot,legoater/skiboot,stewart-ibm/skiboot,stewart-ibm/skiboot,legoater/skiboot,shenki/skiboot,qemu/skiboot,legoater/skiboot,legoater/skiboot,open-power/skiboot,shenki/skiboot,open-power/skiboot,qemu/skiboot,qemu/skiboot,shenki/skiboot,qemu/skiboot,stewart-ibm/skiboot,open-power/skiboot,qemu/skiboot,shenki/skiboot,legoater/skiboot