crypto: caam - free resources in case caam_rng registration failed

Check the return value of the hardware registration for caam_rng and free
resources in case of failure.

Fixes: e24f7c9e ("crypto: caam - hwrng support")
Signed-off-by: Iuliana Prodan <iuliana.prodan@nxp.com>
Reviewed-by: Horia Geanta <horia.geanta@nxp.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>