Revert "st/dri2: Implement DRI2bufferDamageExtension"

This reverts commit 492ffbed.

BACK_LEFT attachment can be outdated when the user calls
KHR_partial_update(), leading to a damage region update on the
wrong pipe_resource object.
Let's not expose the ->set_damage_region() method until the core is
fixed to handle that properly.

Cc: mesa-stable@lists.freedesktop.org
Signed-off-by: Boris Brezillon <boris.brezillon@collabora.com>
Acked-by: Daniel Stone <daniels@collabora.com>