if_bnxt: 50G, 100G and 200G PAM4 support
Add support for 50G, 100G and 200G PAM4 support
Reviewed by: imp
Approved by: imp
Differential revision: https://reviews.freebsd.org/D42959
(cherry picked from commit c63d67e137f353f4bc4d0d56bd793f83204a3e1e)