[SCSI] Rename scsi_print_msg to spi_print_msg

Rename scsi_print_msg to spi_print_msg and move its prototype from
scsi_dbg.h to scsi_transport_spi.h

Signed-off-by: Matthew Wilcox <matthew@wil.cx>
Signed-off-by: James Bottomley <James.Bottomley@SteelEye.com>