drm/vmwgfx: Fix compat mode shader operation

In compat mode, we allowed host-backed user-space with guest-backed
kernel / device. In this mode, set shader commands was broken since
no relocations were emitted. Fix this.

Cc: <stable@vger.kernel.org>
Fixes: e8c66efb

 ("drm/vmwgfx: Make user resource lookups reference-free during validation")
Signed-off-by: Thomas Hellstrom <thellstrom@vmware.com>
Reviewed-by: Brian Paul <brianp@vmware.com>