dma-buf: remove restriction of IOCTL:DMA_BUF_SET_NAME

dma-buf: remove restriction of IOCTL:DMA_BUF_SET_NAME

In this patch(https://patchwork.freedesktop.org/patch/310349),
it add a new IOCTL to support dma-buf user to set debug name.

But it also added a limitation of this IOCTL, it needs the
attachments of dmabuf should be empty, otherwise it will fail.

For the original series, the idea was that allowing name change
mid-use could confuse the users about the dma-buf.
However, the rest of the series also makes sure each dma-buf have a unique
inode(https://patchwork.freedesktop.org/patch/310387/), and any accounting
should probably use that, without relying on the name as much.

So, removing this restriction will let dma-buf userspace users to use it
more comfortably and without any side effect.

Signed-off-by: Guangming Cao <Guangming.Cao@mediatek.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20211014102551.54983-1-guangming.cao@mediatek.com
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Christian König <christian.koenig@amd.com>