bnxt_en: Skip MAC loopback selftest if it is unsupported by FW

bnxt_en: Skip MAC loopback selftest if it is unsupported by FW

Call the new HWRM_PORT_MAC_QCAPS to check if mac loopback is
supported.  Skip the MAC loopback ethtool self test if it is
not supported.

Reviewed-by: Kalesh AP <kalesh-anakkur.purayil@broadcom.com>
Reviewed-by: Pavan Chebbi <pavan.chebbi@broadcom.com>
Reviewed-by: Andy Gospodarek <andrew.gospodarek@broadcom.com>
Signed-off-by: Michael Chan <michael.chan@broadcom.com>
Reviewed-by: Michal Swiatkowski <michal.swiatkowski@linux.intel.com>
Link: https://patch.msgid.link/20241217182620.2454075-5-michael.chan@broadcom.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>