net/bnxt: fix PAM4 mask setting

net/bnxt: fix PAM4 mask setting

Set the PAM4 mask setting only when PAM4 signaling is enabled.
Setting it otherwise seems to result in link negotiation.
Also auto_pam4_link_speeds has been renamed to
auto_pam4_link_speed_mask to reflect its real usage.

Fixes: c23f9ded0391 ("net/bnxt: support 200G PAM4 link")
Cc: stable@dpdk.org
Signed-off-by: Ajit Khaparde <ajit.khaparde@broadcom.com>
Reviewed-by: Kalesh AP <kalesh-anakkur.purayil@broadcom.com>
Reviewed-by: Somnath Kotur <somnath.kotur@broadcom.com>