drivers/gpu/drm/vmwgfx: Fix k.alloc switched arguments

Signed-off-by: Joe Perches <joe@perches.com>
Reviewed-by: Matt Turner <mattst88@gmail.com>
Reviewed-by: Thomas Hellstrom <thellstrom@vmware.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>