scsi: libsas: Declare sas_set_phy_speed() static

sas_set_phy_speed() is used only within sas_init.c. Declare this function
as static.

Signed-off-by: Damien Le Moal <dlemoal@kernel.org>
Link: https://lore.kernel.org/r/20230912230551.454357-3-dlemoal@kernel.org


Reviewed-by: John Garry <john.g.garry@oracle.com>
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>