In 14b4160792 ("vulkan/wsi: Only test for dma-buf sync file support
once"), I moved the dma-buf sync file import/export check earlier. This
is fine for hardware implementations where we have real dma-buf
import/export but it broke lavapipe because the check itself ignored
whether or not we actually have dma-buf import/export. Add a couple
more checks to wsi_drm_check_dma_buf_sync_file_import_export() so it's
safe even for SW drivers. Also, in wsi_create_sync_for_dma_buf_wait(),
check if we actually have a dma-buf.
Fixes: 14b4160792 ("vulkan/wsi: Only test for dma-buf sync file support once")
Reviewed-by: Mike Blumenkrantz <michael.blumenkrantz@gmail.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/37033>
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