scsi: atari_scsi: Use m68k_realnum_memory for FastRAM test

m68k_num_memory is unsuitable to test for the presence of FastRAM on
CT60 if the kernel is located in FastRAM: in arch/m68k/mm/motorola.c the
ST-RAM chunk is skipped and m68k_num_memory is decremented in this
case. m68k_realnum_memory still contains the actual number of RAM chunks
so use that.
Signed-off-by: Michael Schmitz <schmitzmic@gmail.com>
Tested-by: Christian T. Steigies <cts@debian.org>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

drivers/scsi/atari_scsi.c

@@ -776,7 +776,7 @@ static int __init atari_scsi_probe(struct platform_device *pdev)
 	 * from/to alternative Ram.
 	 */
 	if (ATARIHW_PRESENT(ST_SCSI) && !ATARIHW_PRESENT(EXTD_DMA) &&
-	    m68k_num_memory > 1) {
+	    m68k_realnum_memory > 1) {
 		atari_dma_buffer = atari_stram_alloc(STRAM_BUFFER_SIZE, "SCSI");
 		if (!atari_dma_buffer) {
 			pr_err(PFX "can't allocate ST-RAM double buffer\n");