arm/arm64: crypto: assure that ECB modes don't require an IV

ECB modes don't use an initialization vector. The kernel
/proc/crypto interface doesn't reflect this properly.

Acked-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Jeremy Linton <jeremy.linton@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>