backends/drm: use GBM_BO_USE_SCANOUT when importing buffers for multi gpu
The gbm surface may not have the scanout use flag, and if the buffer is imported without it, creating the framebuffer may fail CCBUG: 454086
The gbm surface may not have the scanout use flag, and if the buffer is imported without it, creating the framebuffer may fail CCBUG: 454086
mentioned in commit 9baa2c3e
·mentioned in commit 9baa2c3e