drm/vmwgfx: Remove unused code

Remove unused structs, members, and file. Many of these are written but
never read.

Signed-off-by: Ian Forbes <ian.forbes@broadcom.com>
Signed-off-by: Zack Rusin <zack.rusin@broadcom.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240214210440.26167-1-ian.forbes@broadcom.com