scsi: core: Unexport scsi_bus_type

scsi_bus_type is not used by any code outside of scsi_mod.ko.

Link: https://lore.kernel.org/r/20220523083838.227987-1-hch@lst.de


Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>