kernel: vfio: flag vfio_virqfd as only kernel 6.2 and earlier

Kernel 6.2 folded virqfd (eventd interface for VFIO interrupts)
into the base vfio module, it is no longer a tristate option.

Change suggested by vincejv on GitHub:
openwrt#14868 (comment)

Signed-off-by: Mathew McBride <matt@traverse.com.au>

package/kernel/linux/modules/virt.mk

@@ -84,9 +84,9 @@ define KernelPackage/vfio
 	CONFIG_VFIO_MDEV=n
   FILES:= \
 	$(LINUX_DIR)/drivers/vfio/vfio.ko \
-	$(LINUX_DIR)/drivers/vfio/vfio_virqfd.ko \
+	$(LINUX_DIR)/drivers/vfio/vfio_virqfd.ko@lt6.2 \
 	$(LINUX_DIR)/drivers/vfio/vfio_iommu_type1.ko
-  AUTOLOAD:=$(call AutoProbe,vfio vfio_iommu_type1 vfio_virqfd)
+  AUTOLOAD:=$(call AutoProbe,vfio vfio_iommu_type1 +LINUX_6_1:vfio_virqfd)
 endef
 
 define KernelPackage/vfio/description