crypto: qat - Fix unsigned function returning negative constant

The function qat_uclo_check_image_compat has an unsigned return type, but
returns a negative constant to indicate an error condition. So we change
unsigned to int.

Signed-off-by: Haowen Bai <baihaowen@meizu.com>
Acked-by: Giovanni Cabiddu <giovanni.cabiddu@intel.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>