drm/vmwgfx: Fix hash key computation

The hash key computation in vmw_cmdbuf_res_remove incorrectly didn't take
the resource type into account, contrary to all the other related functions.
This becomes important when the cmdbuf resource manager handles more than
one resource type.

Signed-off-by: Thomas Hellstrom <thellstrom@vmware.com>
Reviewed-by: Brian Paul <brianp@vmware.com>