vfio/cdx: update driver to build without CONFIG_GENERIC_MSI_IRQ

Define dummy MSI related APIs in VFIO CDX driver to build the
driver without enabling CONFIG_GENERIC_MSI_IRQ flag.

Reported-by: kernel test robot <[e-mail]>
Closes: https://lore.kernel.org/oe-kbuild-all/[e-mail]/
Reviewed-by: Nikhil Agarwal <[e-mail]>
Reviewed-by: Alex Williamson <[e-mail]>
Signed-off-by: Nipun Gupta <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Alex Williamson <[e-mail]>

drivers/vfio/cdx/Makefile

···
 
 obj-$(CONFIG_VFIO_CDX) += vfio-cdx.o
 
-vfio-cdx-objs := main.o intr.o
+vfio-cdx-objs := main.o
+
+ifdef CONFIG_GENERIC_MSI_IRQ
+vfio-cdx-objs += intr.o
+endif

drivers/vfio/cdx/private.h

···
 	u8			config_msi;
 };
 
+#ifdef CONFIG_GENERIC_MSI_IRQ
 int vfio_cdx_set_irqs_ioctl(struct vfio_cdx_device *vdev,
 			    u32 flags, unsigned int index,
 			    unsigned int start, unsigned int count,
 			    void *data);
 
 void vfio_cdx_irqs_cleanup(struct vfio_cdx_device *vdev);
+#else
+static int vfio_cdx_set_irqs_ioctl(struct vfio_cdx_device *vdev,
+				   u32 flags, unsigned int index,
+				   unsigned int start, unsigned int count,
+				   void *data)
+{
+	return -EINVAL;
+}
+
+static void vfio_cdx_irqs_cleanup(struct vfio_cdx_device *vdev)
+{
+}
+#endif
 
 #endif /* VFIO_CDX_PRIVATE_H */