drm/vmwgfx: Add basic support for SVGA3

SVGA3 is the next version of our PCI device. Some of the changes
include using MMIO for register accesses instead of ioports,
deprecating the FIFO MMIO and removing a lot of the old and
legacy functionality. SVGA3 doesn't support guest backed
objects right now so everything except 3D is working.

v2: Fixes all the static analyzer warnings

Signed-off-by: Zack Rusin <zackr@vmware.com>
Cc: Martin Krastev <krastevm@vmware.com>
Reviewed-by: Roland Scheidegger <sroland@vmware.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210505191007.305872-1-zackr@vmware.com