In case memory resources for *base* were allocated, release them
before return.

Addresses-Coverity-ID: 1471702 ("Resource leak")
Fixes: e3fe0ae1 ("crypto: dh - add public key verification test")
Signed-off-by: NGustavo A. R. Silva <gustavo@embeddedor.com>
Reviewed-by: NStephan Müller <smueller@chronox.de>
Signed-off-by: NHerbert Xu <herbert@gondor.apana.org.au>