crypto: testmgr - fix sizeof() on COMP_BUF_SIZE

After allocation, output and decomp_output both point to memory chunks of
size COMP_BUF_SIZE. Then, only the first bytes are zeroed out using
sizeof(COMP_BUF_SIZE) as parameter to memset(), because
sizeof(COMP_BUF_SIZE) provides the size of the constant and not the size of
allocated memory.

Instead, the whole allocated memory is meant to be zeroed out. Use
COMP_BUF_SIZE as parameter to memset() directly in order to accomplish
this.

Fixes: 33607384

 ("crypto: testmgr - Allow different compression results")

Signed-off-by: Michael Schupikov <michael@schupikov.de>
Reviewed-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>