drm/vmwgfx: Fix a bad merge in otable batch takedown

Change
2ef4fb92 ("drm/vmwgfx: Make sure bo's are unpinned before putting them back")
caused a conflict in one of the drm trees and the merge commit
68a32ba1 ("Merge tag 'drm-next-2021-04-28' of git://anongit.freedesktop.org/drm/drm")
accidently re-added code that the original change was removing.
Fixed by removing the incorrect buffer unpin - it has already been unpinned
two lines above.

Fixes: 68a32ba1

 ("Merge tag 'drm-next-2021-04-28' of git://anongit.freedesktop.org/drm/drm")
Signed-off-by: Zack Rusin <zackr@vmware.com>
Reviewed-by: Martin Krastev <krastevm@vmware.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210615182336.995192-4-zackr@vmware.com