drm/xe/pf: fix VFIO link error

The Makefile logic for building xe_sriov_vfio.o was added incorrectly,
as setting CONFIG_XE_VFIO_PCI=m means it doesn't get included into a
built-in xe driver:

ERROR: modpost: "xe_sriov_vfio_stop_copy_enter" [drivers/vfio/pci/xe/xe-vfio-pci.ko] undefined!
ERROR: modpost: "xe_sriov_vfio_stop_copy_exit" [drivers/vfio/pci/xe/xe-vfio-pci.ko] undefined!
ERROR: modpost: "xe_sriov_vfio_suspend_device" [drivers/vfio/pci/xe/xe-vfio-pci.ko] undefined!
ERROR: modpost: "xe_sriov_vfio_wait_flr_done" [drivers/vfio/pci/xe/xe-vfio-pci.ko] undefined!
ERROR: modpost: "xe_sriov_vfio_error" [drivers/vfio/pci/xe/xe-vfio-pci.ko] undefined!
ERROR: modpost: "xe_sriov_vfio_resume_data_enter" [drivers/vfio/pci/xe/xe-vfio-pci.ko] undefined!
ERROR: modpost: "xe_sriov_vfio_resume_device" [drivers/vfio/pci/xe/xe-vfio-pci.ko] undefined!
ERROR: modpost: "xe_sriov_vfio_resume_data_exit" [drivers/vfio/pci/xe/xe-vfio-pci.ko] undefined!
ERROR: modpost: "xe_sriov_vfio_data_write" [drivers/vfio/pci/xe/xe-vfio-pci.ko] undefined!
ERROR: modpost: "xe_sriov_vfio_migration_supported" [drivers/vfio/pci/xe/xe-vfio-pci.ko] undefined!
WARNING: modpost: suppressed 3 unresolved symbol warnings because there were too many)

Check for CONFIG_XE_VFIO_PCI being enabled in the Makefile to decide whether to
include the object instead.

Fixes: bd45d46 ("drm/xe/pf: Export helpers for VFIO")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Michal Wajdeczko <michal.wajdeczko@intel.com>
Signed-off-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Link: https://patch.msgid.link/20251204094154.1029357-1-arnd@kernel.org
(cherry picked from commit ef7de33)
Signed-off-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>

Author: arndb

drivers/gpu/drm/xe/Makefile

@@ -184,8 +184,8 @@ xe-$(CONFIG_PCI_IOV) += \
 	xe_sriov_pf_sysfs.o \
 	xe_tile_sriov_pf_debugfs.o
 
-ifeq ($(CONFIG_PCI_IOV),y)
-	xe-$(CONFIG_XE_VFIO_PCI) += xe_sriov_vfio.o
+ifdef CONFIG_XE_VFIO_PCI
+	xe-$(CONFIG_PCI_IOV) += xe_sriov_vfio.o
 endif
 
 # include helpers for tests even when XE is built-in