drm/vmwgfx: remove redundant return ret statement

The return statement is redundant as there is a return statement
immediately before it so we have dead code that can be removed.
Also remove the unused declaration of ret.

Detected by CoverityScan, CID#1473793 ("Structurally dead code")

Signed-off-by: Colin Ian King <colin.king@canonical.com>
Reviewed-by: Thomas Hellstrom <thellstrom@vmware.com>
Signed-off-by: Thomas Hellstrom <thellstrom@vmware.com>