bnxt_en: Add 100G link speed reporting for BCM57454 ASIC in ethtool

Added support for 100G link speed reporting for Broadcom BCM57454
ASIC in ethtool command.

Signed-off-by: Deepak Khungar <deepak.khungar@broadcom.com>
Signed-off-by: Ray Jui <ray.jui@broadcom.com>
Signed-off-by: Michael Chan <michael.chan@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>