drm/radeon: evergreen/cayman indirect draw support (v2)

Add the necessary set of commands to support OpenGL
indirect draw calls on evergreen/cayman devices that
do not have VM.

v2: agd5f: fix warning on 32-bit

Reviewed-by: Marek Olšák <marek.olsak@amd.com>
Signed-off-by: Glenn Kennard <glenn.kennard@gmail.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>