Unify common BNXT and MLX5 initialization code (#233)

Co-authored-by: Aurelien Bouteiller <aurelien.bouteiller@amd.com>

scripts/build_configs/gda_mlx5

@@ -27,4 +27,4 @@ set -e
 
 script_path=$(dirname "$(realpath $0)")
 
-exec $script_path/gda $*
+source $script_path/gda -DGDA_MLX5=ON $*