crypto: caam - invalidate entropy register during RNG initialization

In order to make sure that we always use non-stale entropy data, change
the code to invalidate entropy register during RNG initialization.

Signed-off-by: Aymen Sghaier <aymen.sghaier@nxp.com>
Signed-off-by: Vipul Kumar <vipul_kumar@mentor.com>
[andrew.smirnov@gmail.com ported to upstream kernel, rewrote commit msg]
Signed-off-by: Andrey Smirnov <andrew.smirnov@gmail.com>
Reviewed-by: Horia Geantă <horia.geanta@nxp.com>
Cc: Chris Healy <cphealy@gmail.com>
Cc: Lucas Stach <l.stach@pengutronix.de>
Cc: Horia Geantă <horia.geanta@nxp.com>
Cc: Herbert Xu <herbert@gondor.apana.org.au>
Cc: Iuliana Prodan <iuliana.prodan@nxp.com>
Cc: linux-crypto@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Cc: linux-imx@nxp.com
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>