crypto: caam - do not use mem and emi_slow clock for imx7x

I.MX7x only use two clocks for the CAAM module, so make sure we do not try to
use the mem and the emi_slow clock when running in that imx7d and imx7s machine
type.

Cc: "Horia Geantă" <horia.geanta@nxp.com>
Cc: Aymen Sghaier <aymen.sghaier@nxp.com>
Cc: Fabio Estevam <fabio.estevam@nxp.com>
Cc: Peng Fan <peng.fan@nxp.com>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Lukas Auer <lukas.auer@aisec.fraunhofer.de>
Signed-off-by: Rui Miguel Silva <rui.silva@linaro.org>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>