[SCSI] sun3: Check for NCR_TIMEOUT being defined instead of having a value

This fixes:

drivers/scsi/sun3_NCR5380.c:1448:5: warning: "NCR_TIMEOUT" is not defined

Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: James Bottomley <JBottomley@Parallels.com>