util/vfio-helpers: Improve reporting unsupported IOMMU type

Change the confuse "VFIO IOMMU check failed" error message by
the explicit "VFIO IOMMU Type1 is not supported" once.

Example on POWER:

 $ qemu-system-ppc64 -drive if=none,id=nvme0,file=nvme://0001:01:00.0/1,format=raw
 qemu-system-ppc64: -drive if=none,id=nvme0,file=nvme://0001:01:00.0/1,format=raw: VFIO IOMMU Type1 is not supported

Suggested-by: Alex Williamson <alex.williamson@redhat.com>
Reviewed-by: Fam Zheng <fam@euphon.net>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Message-id: 20201103020733.2303148-2-philmd@redhat.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Tested-by: Eric Auger <eric.auger@redhat.com>

util/vfio-helpers.c

@@ -300,7 +300,7 @@ static int qemu_vfio_init_pci(QEMUVFIOState *s, const char *device,
     }
 
     if (!ioctl(s->container, VFIO_CHECK_EXTENSION, VFIO_TYPE1_IOMMU)) {
-        error_setg_errno(errp, errno, "VFIO IOMMU check failed");
+        error_setg_errno(errp, errno, "VFIO IOMMU Type1 is not supported");
         ret = -EINVAL;
         goto fail_container;
     }