scsi: sd: Fix typo in sd_first_printk()

Commit b2bff6ce ("[SCSI] sd: Quiesce mode sense error messages")
added the macro sd_first_printk(). The macro takes "sdsk" as argument
but dereferences "sdkp". This hasn't caused any real issues since all
callers of sd_first_printk() have an sdkp. But fix the typo.

[mkp: Turned this into a real patch and tweaked commit description]
Signed-off-by: Dietmar Hahn <dietmar.hahn@ts.fujitsu.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

drivers/scsi/sd.h

@@ -132,7 +132,7 @@ static inline struct scsi_disk *scsi_disk(struct gendisk *disk)
 
 #define sd_first_printk(prefix, sdsk, fmt, a...)			\
 	do {								\
-		if ((sdkp)->first_scan)					\
+		if ((sdsk)->first_scan)					\
 			sd_printk(prefix, sdsk, fmt, ##a);		\
 	} while (0)