scsi: scsi_transport_spi: make two const arrays static, shrinks object size

Don't populate the const read-only arrays spi_test_unit_ready and
spi_test_unit_ready on the stack but instead make them static. Makes the
object code smaller by over 100 bytes:

Before:
   text	   data	    bss	    dec	    hex	filename
  40171	  12832	    128	  53131	   cf8b	drivers/scsi/scsi_transport_spi.o

After:
   text	   data	    bss	    dec	    hex	filename
  39922	  12976	    128	  53026	   cf22	drivers/scsi/scsi_transport_spi.o

(gcc version 7.2.0 x86_64)
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

drivers/scsi/scsi_transport_spi.c

@@ -822,11 +822,11 @@ spi_dv_device_get_echo_buffer(struct scsi_device *sdev, u8 *buffer)
 	 * fails, the device won't let us write to the echo buffer
 	 * so just return failure */
 	
-	const char spi_test_unit_ready[] = {
+	static const char spi_test_unit_ready[] = {
 		TEST_UNIT_READY, 0, 0, 0, 0, 0
 	};
 
-	const char spi_read_buffer_descriptor[] = {
+	static const char spi_read_buffer_descriptor[] = {
 		READ_BUFFER, 0x0b, 0, 0, 0, 0, 0, 0, 4, 0
 	};