virtio-gpu-udmabuf: create udmabuf for blob even when iov_cnt == 1

virtio-gpu-udmabuf: create udmabuf for blob even when iov_cnt == 1

There were often cases where a scanout blob sometimes has just 1 entry
that is linked to many pages in it. So just checking whether iov_cnt is 1
is not enough for screening small, non-scanout blobs. Therefore adding
iov_len check as well to make sure it creates an udmabuf only for a scanout
blob, which is at least bigger than one page size.

Cc: Gerd Hoffmann <kraxel@redhat.com>
Cc: Marc-André Lureau <marcandre.lureau@redhat.com>
Cc: Vivek Kasireddy <vivek.kasireddy@intel.com>
Signed-off-by: Dongwon Kim <dongwon.kim@intel.com>
Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Message-ID: <20230621222704.29932-1-dongwon.kim@intel.com>