staging: fsl-mc: remove slab cache for mc devices

Let's drop the slab cache for objects
until we actually have proof that it improves
performance. This makes the code cleaner.

Signed-off-by: Laurentiu Tudor <laurentiu.tudor@nxp.com>
Acked-by: Stuart Yoder <stuart.yoder@nxp.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>