drm/vmwgfx: Fix fencing on SVGAv3

drm/vmwgfx: Fix fencing on SVGAv3

[ Upstream commit 1d6595b4cd47acfd824550f48f10b54a6f0e93ee ]

Port of the vmwgfx to SVGAv3 lacked support for fencing. SVGAv3 removed
FIFO's and replaced them with command buffers and extra registers.
The initial version of SVGAv3 lacked support for most advanced features
(e.g. 3D) which made fences unnecessary. That is no longer the case,
especially as 3D support is being turned on.

Switch from FIFO commands and capabilities to command buffers and extra
registers to enable fences on SVGAv3.

Fixes: 2cd80dbd3551 ("drm/vmwgfx: Add basic support for SVGA3")
Signed-off-by: Zack Rusin <zackr@vmware.com>
Reviewed-by: Martin Krastev <krastevm@vmware.com>
Reviewed-by: Maaz Mombasawala <mombasawalam@vmware.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220302152426.885214-5-zack@kde.org
Signed-off-by: Sasha Levin <sashal@kernel.org>