Simplify SR-IOV VFIO driver check logic

- Remove unnecessary conditional check in sriov_attach_detach_device_vfio_variant_driver.py
- The check_vfio_pci function can handle None values for exp_driver parameter
- Reduces code complexity from 4 lines to 1 line

Signed-off-by: hholoubk <[email protected]>

AI assisted code and commit. Human reviewed.

Author: hholoubk

libvirt/tests/src/sriov/plug_unplug/sriov_attach_detach_device_vfio_variant_driver.py

@@ -81,10 +81,7 @@ def parse_iface_dict(pf_pci):
             test.log.debug(f"Actual XML: {actual_vm_hostdev}")
             if act_hostdev_dict.get("driver")["driver_attr"].get("name") != "vfio":
                 test.fail("The hostdev driver is not set to VFIO.")
-            if expr_driver:
-                libvirt_vfio.check_vfio_pci(vf_pci, exp_driver=expr_driver)
-            else:
-                libvirt_vfio.check_vfio_pci(vf_pci)
+            libvirt_vfio.check_vfio_pci(vf_pci, exp_driver=expr_driver)
 
         test.log.info("TEST_STEP: ping test from VM to outside")
         if sriov_vfio.is_linked(pf_name=test_pf) and ping_dest: