scsi: esp_scsi: Correct ordering of PCSCSI definition in esp_rev enum

The order of the definitions in the esp_rev enum is important. The values
are used in comparisons for chip features.

Add a comment to the enum explaining this.

Also, the actual values for the enum fields are irrelevant, so remove the
explicit values (suggested by Geert Uytterhoeven). This makes adding a new
field in the middle of the enum easier.

Finally, move the PCSCSI definition to the right place in the enum. In its
previous location, at the end of the enum, the wrong values are written to
the CONFIG3 register when used with FAST-SCSI targets.

Link: https://lore.kernel.org/r/20191119202021.28720-2-jongk@linux-m68k.org
Signed-off-by: Kars de Jong <jongk@linux-m68k.org>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

drivers/scsi/esp_scsi.c

@@ -2373,10 +2373,10 @@ static const char *esp_chip_names[] = {
 	"ESP100A",
 	"ESP236",
 	"FAS236",
+	"AM53C974",
 	"FAS100A",
 	"FAST",
 	"FASHME",
-	"AM53C974",
 };
 
 static struct scsi_transport_template *esp_transport_template;

drivers/scsi/esp_scsi.h

@@ -257,15 +257,16 @@ struct esp_cmd_priv {
 };
 #define ESP_CMD_PRIV(CMD)	((struct esp_cmd_priv *)(&(CMD)->SCp))
 
+/* NOTE: this enum is ordered based on chip features! */
 enum esp_rev {
-	ESP100     = 0x00,  /* NCR53C90 - very broken */
-	ESP100A    = 0x01,  /* NCR53C90A */
-	ESP236     = 0x02,
-	FAS236     = 0x03,
-	FAS100A    = 0x04,
-	FAST       = 0x05,
-	FASHME     = 0x06,
-	PCSCSI     = 0x07,  /* AM53c974 */
+	ESP100,  /* NCR53C90 - very broken */
+	ESP100A, /* NCR53C90A */
+	ESP236,
+	FAS236,
+	PCSCSI,  /* AM53c974 */
+	FAS100A,
+	FAST,
+	FASHME,
 };
 
 struct esp_cmd_entry {