drivers: fix build of crypto anonymous union initialization

drivers: fix build of crypto anonymous union initialization

In SUSE11-SP3 i686 platform, with gcc 4.5.1, there are compile issues, e.g:
  null_crypto_pmd_ops.c:44:3: error:
  unknown field 'sym' specified in initializer
  cc1: warnings being treated as errors

The member in anonymous union initialization should be inside '{}',
otherwise it will report an error.

Fixes: 26c2e4ad5ad4 ("cryptodev: add capabilities discovery")

Signed-off-by: Michael Qiu <michael.qiu@intel.com>
Signed-off-by: Fiona Trahe <fiona.trahe@intel.com>