crypto: caam - Add check for kcalloc() in test_len()

crypto: caam - Add check for kcalloc() in test_len()

As kcalloc() may fail, check its return value to avoid a NULL pointer
dereference when passing the buffer to rng->read(). On allocation
failure, log the error and return since test_len() returns void.

Fixes: 2be0d806e25e ("crypto: caam - add a test for the RNG")
Cc: stable@vger.kernel.org
Signed-off-by: Guangshuo Li <lgs201920130244@gmail.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>