bnxt_en: Add missing 200G link speed reporting

bnxt_fw_to_ethtool_speed() is missing the case statement for 200G
link speed reported by firmware.  As a result, ethtool will report
unknown speed when the firmware reports 200G link speed.

Fixes: 532262ba

 ("bnxt_en: ethtool: support PAM4 link speeds up to 200G")
Signed-off-by: Michael Chan <michael.chan@broadcom.com>
Reviewed-by: Simon Horman <simon.horman@corigine.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>