crypto: compress - Return produced bytes in crypto_{,de}compress_{update,final}

If crypto_{,de}compress_{update,final}() succeed, return the actual number of
bytes produced instead of zero, so their users don't have to calculate that
theirselves.

Signed-off-by: Geert Uytterhoeven <Geert.Uytterhoeven@sonycom.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>