PCI: Add missing MODULE_DESCRIPTION() macros

When ARCH=x86, make allmodconfig && make W=1 C=1 reports:

  WARNING: modpost: missing MODULE_DESCRIPTION() in drivers/pci/pci-stub.o
  WARNING: modpost: missing MODULE_DESCRIPTION() in drivers/pci/pci-pf-stub.o

Add the missing MODULE_DESCRIPTION() macro.

Link: https://lore.kernel.org/r/20240610-md-drivers-pci-v1-1-139c135853ea@quicinc.com
Signed-off-by: Jeff Johnson <quic_jjohnson@quicinc.com>
[bhelgaas: update MODULE_DESCRIPTION() text]
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Signed-off-by: Krzysztof Wilczyński <kwilczynski@kernel.org>

Author: Jeff Johnson

drivers/pci/pci-pf-stub.c

@@ -39,4 +39,5 @@ static struct pci_driver pf_stub_driver = {
 };
 module_pci_driver(pf_stub_driver);
 
+MODULE_DESCRIPTION("SR-IOV PF stub driver with no functionality");
 MODULE_LICENSE("GPL");

drivers/pci/pci-stub.c

@@ -92,5 +92,6 @@ static void __exit pci_stub_exit(void)
 module_init(pci_stub_init);
 module_exit(pci_stub_exit);
 
+MODULE_DESCRIPTION("VM device assignment stub driver");
 MODULE_LICENSE("GPL");
 MODULE_AUTHOR("Chris Wright <chrisw@sous-sol.org>");