The comment for the deflate test vectors says the winbits parameter is 11,
while the deflate module actually uses -11 (a negative window bits parameter
enables the raw deflate format instead of the zlib format).
Correct this, to avoid confusion about the format used.

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