scsi: core: Declare 'scsi_scan_type' static

'scsi_scan_type' is only used in one source file. Hence declare it static.

Link: https://lore.kernel.org/r/20211129194609.3466071-3-bvanassche@acm.org


Fixes: a19a93e4 ("scsi: core: pm: Rely on the device driver core for async power management")
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>