scsi: update scsi.h with SYNCHRONIZE_CACHE_16

It's in SBC-3.
Signed-off-by: Andy Grover <agrover@redhat.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: James Bottomley <JBottomley@Parallels.com>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>

include/scsi/scsi.h

@@ -143,6 +143,7 @@ struct scsi_cmnd;
 #define READ_ATTRIBUTE        0x8c
 #define WRITE_ATTRIBUTE	      0x8d
 #define VERIFY_16	      0x8f
+#define SYNCHRONIZE_CACHE_16  0x91
 #define WRITE_SAME_16	      0x93
 #define SERVICE_ACTION_IN     0x9e
 /* values for service action in */