drm/vmwgfx: Cleanup the cursor snooping code

Cursor snooping depended on implicit size and format which made debugging
quite difficult. Make the code easier to following by making everything
explicit and instead of using magic numbers predefine all the
parameters the code depends on.

Also fixes incorrectly computed pitches for non-aligned cursor snoops.
Fix which has no practical effect because non-aligned cursor snoops
are not used by the X11 driver and Wayland cursors will go through
mob cursors, instead of surface dma's.

Signed-off-by: Zack Rusin <zackr@vmware.com>
Reviewed-by: Michael Banack <banackm@vmware.com>
Reviewed-by: Martin Krastev <krastevm@vmware.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20221026031936.1004280-2-zack@kde.org