crypto: ixp4xx - Do not check word size when compile testing

The BUILD_BUG_ON preventing compilation on foreign architectures
should be disabled when we're doing compile testing.

Fixes: 1bc7fdbf ("crypto: ixp4xx - Move driver to...")
Reported-by: kernel test robot <lkp@intel.com>
Link: https://lore.kernel.org/oe-kbuild-all/202304061846.G6cpPXiQ-lkp@intel.com/


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