CVE-2022-50614 misc: pci_endpoint_test: Fix pci_endpoint_test_{copy,write,read}() panic

In the Linux kernel, the following vulnerability has been resolved: misc: pciendpointtest: Fix pciendpointtestcopy,write,read panic The dmamapsingle doesn't permit zero length mapping. It causes a follow panic. A panic was reported on arm64: 60.137988 ------------ cut here ------------ 60.142630...