scsi: pm80xx: Add helper function to get the local phy id

Avoid duplicated code by adding a helper to get the local phy id.

No functional changes intended.

Signed-off-by: Niklas Cassel <cassel@kernel.org>
Link: https://lore.kernel.org/r/20250814173215.1765055-20-cassel@kernel.org


Reviewed-by: Damien Le Moal <dlemoal@kernel.org>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>