misc: pci_endpoint_test: Fix array underflow in pci_endpoint_test_ioctl()

In the Linux kernel, the following vulnerability has been resolved: misc: pci_endpoint_test: Fix array underflow in pci_endpoint_test_ioctl() Commit eefb83790a0d ("misc: pci_endpoint_test: Add doorbell test case") added NO_BAR (-1) to the pci_barno enum which, in practical terms, changes the enum from an unsigned int to a signed int. If the user passes a negative number in pci_endpoint_test_ioctl() then it results in an array underflow in pci_endpoint_test_bar().