common/mlx5: extend flex parser capabilities

common/mlx5: extend flex parser capabilities

MLX5 PARSE_GRAPH_NODE is the main data structure used by the Flex
Parser when a new parsing protocol is defined. While software
creates PARSE_GRAPH_NODE object for a new protocol, it must
verify that configuration parameters it uses comply with
hardware limits.

The patch queries hardware PARSE_GRAPH_NODE capabilities and
stores ones in PMD internal configuration structure:

 - query capabilities from parse_graph_node attribute page
 - query max_num_prog_sample_field capability from HCA page 2

Signed-off-by: Gregory Etelson <getelson@nvidia.com>
Reviewed-by: Viacheslav Ovsiienko <viacheslavo@nvidia.com>