backend-drm: Add GBM_BO_HANDLE as a failure reason

And use it to get a feedback event for when adding scanout tranche.

With this change, I get back a feedback event for dmabuf-feedback
on VC4:

���� tranche: target device /dev/dri/card0, scanout
�   ���� format ABGR2101010, modifier LINEAR (0x0)
�   ���� format XBGR2101010, modifier LINEAR (0x0)
�   ���� format ARGB8888, modifier LINEAR (0x0)
�   ���� format ABGR8888, modifier LINEAR (0x0)
�   ���� format XRGB8888, modifier LINEAR (0x0)
�   ���� format XBGR8888, modifier LINEAR (0x0)
�   ���� format RGB565, modifier LINEAR (0x0)
�   ���� format YUV420, modifier LINEAR (0x0)
�   ���� format YUV422, modifier LINEAR (0x0)
�   ���� format YVU420, modifier LINEAR (0x0)
�   ���� format YVU422, modifier LINEAR (0x0)
�   ���� format NV12, modifier LINEAR (0x0)
�   ���� format NV12, modifier BROADCOM_SAND128 (0x700000000000004)
�   ���� format NV16, modifier LINEAR (0x0)
�   ���� end of tranche

Besides that, it can place a fullscreen state of simple-egl on the
primary plane, which without this change wasn't possible.

Signed-off-by: Marius Vlad <marius.vlad@collabora.com>