acl: optimize AVX512 classify with 4 bytes loads

acl: optimize AVX512 classify with 4 bytes loads

With current ACL implementation first field in the rule definition
has always to be one byte long. Though for optimising classify
implementation it might be useful to do 4B reads
(as we do for rest of the fields).
So at build phase, check user provided field definitions to determine
is it safe to do 4B loads for first ACL field.
Then at run-time this information can be used to choose classify
behavior.

Signed-off-by: Konstantin Ananyev <konstantin.ananyev@intel.com>