ata: ahci: Add debug print for external port

Add a debug print that tells us if LPM is not getting enabled because the
port is external.

Reviewed-by: Damien Le Moal <dlemoal@kernel.org>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
Link: https://lore.kernel.org/r/20240703184418.723066-20-cassel@kernel.org


Signed-off-by: Niklas Cassel <cassel@kernel.org>