crypto: crypto4xx - fix double-free in crypto4xx_destroy_sdr

This patch fixes a crash that can happen during probe
when the available dma memory is not enough (this can
happen if the crypto4xx is built as a module).

The descriptor window mapping would end up being free'd
twice, once in crypto4xx_build_pdr() and the second time
in crypto4xx_destroy_sdr().

Fixes: 5d59ad6e

 ("crypto: crypto4xx - fix crypto4xx_build_pdr, crypto4xx_build_sdr leak")
Cc: <stable@vger.kernel.org>
Signed-off-by: Christian Lamparter <chunkeey@gmail.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>