bnxt_en: Skip PHY loopback ethtool selftest if unsupported by FW

bnxt_en: Skip PHY loopback ethtool selftest if unsupported by FW

Skip PHY loopback selftest if firmware advertises that it is unsupported
in the HWRM_PORT_PHY_QCAPS call.  Only show PHY loopback test result to
be 0 if the test has run and passes.  Do the same for external loopback
to be consistent.

Reviewed-by: Pavan Chebbi <pavan.chebbi@broadcom.com>
Reviewed-by: Kalesh AP <kalesh-anakkur.purayil@broadcom.com>
Signed-off-by: Michael Chan <michael.chan@broadcom.com>
Link: https://patch.msgid.link/20241217182620.2454075-4-michael.chan@broadcom.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>