CVE-2021-47005 PCI: endpoint: Fix NULL pointer dereference for ->get_features()

In the Linux kernel, the following vulnerability has been resolved: PCI: endpoint: Fix NULL pointer dereference for -getfeatures getfeatures ops of pciepcops may return NULL, causing NULL pointer dereference in pciepftestallocspace function. Let us add a check for pciepcfeature pointer in...