bng_en: query PHY capabilities and report link status

bng_en: query PHY capabilities and report link status

Query PHY capabilities and supported speeds from firmware,
retrieve current link state (speed, duplex, pause, FEC),
and log the information. Seed initial link state during probe.

Signed-off-by: Bhargava Marreddy <bhargava.marreddy@broadcom.com>
Reviewed-by: Vikas Gupta <vikas.gupta@broadcom.com>
Reviewed-by: Rajashekar Hudumula <rajashekar.hudumula@broadcom.com>
Reviewed-by: Ajit Kumar Khaparde <ajit.khaparde@broadcom.com>
Link: https://patch.msgid.link/20260406180420.279470-3-bhargava.marreddy@broadcom.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>