bnxt_en: Implement ethtool .set_tunable() for ETHTOOL_PFC_PREVENTION_TOUT

bnxt_en: Implement ethtool .set_tunable() for ETHTOOL_PFC_PREVENTION_TOUT

Support the setting of the tunable if it is supported by firmware.
The supported range is 0 to the maximum msec value reported by
firmware.  PFC_STORM_PREVENTION_AUTO is also supported and 0 means it
is disabled.

Reviewed-by: Andy Gospodarek <andrew.gospodarek@broadcom.com>
Signed-off-by: Michael Chan <michael.chan@broadcom.com>
Link: https://patch.msgid.link/20250917040839.1924698-11-michael.chan@broadcom.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>