crypto: inside-secure - remove useless memset

This patch removes an useless memset in the ahash_export function, as
the zeroed buffer will be entirely overridden the next line.

Suggested-by: Ofer Heifetz <oferh@marvell.com>
Signed-off-by: Antoine Tenart <antoine.tenart@free-electrons.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>