[PATCH] Correct typo in linux/scsi/scsi.h and introduce new

I notice we seem to have a typo in the SAM_ status codes (they say
IMMEDIATE where they mean INTERMEDIATE).

I've also introduced a new macro who's job is to return true if any of
the possible good return codes is found.  This means

SAM_STAT_GOOD
SAM_STAT_INTERMEDIATE
SAM_STAT_INTERMEDIATE_CONDITION_MET

and for now

SAM_STAT_COMMAND_TERMINATED

By and large, this is currently irrelevant to us, since we don't use
linked commands and I've never met a device using COMMAND TERMINATED,
but it may help us in the future.

include/scsi/scsi.h

@@ -111,14 +111,39 @@ extern const unsigned char scsi_command_size[8];
 #define SAM_STAT_CHECK_CONDITION 0x02
 #define SAM_STAT_CONDITION_MET   0x04
 #define SAM_STAT_BUSY            0x08
-#define SAM_STAT_IMMEDIATE       0x10
-#define SAM_STAT_IMMEDIATE_CONDITION_MET 0x14
+#define SAM_STAT_INTERMEDIATE    0x10
+#define SAM_STAT_INTERMEDIATE_CONDITION_MET 0x14
 #define SAM_STAT_RESERVATION_CONFLICT 0x18
 #define SAM_STAT_COMMAND_TERMINATED 0x22	/* obsolete in SAM-3 */
 #define SAM_STAT_TASK_SET_FULL   0x28
 #define SAM_STAT_ACA_ACTIVE      0x30
 #define SAM_STAT_TASK_ABORTED    0x40
 
+/** scsi_status_is_good - check the status return.
+ *
+ * @status: the status passed up from the driver (including host and
+ *          driver components)
+ *
+ * This returns true for known good conditions that may be treated as
+ * command completed normally
+ */
+static inline int scsi_status_is_good(int status)
+{
+	/* mask out the relevant bits
+	 *
+	 * FIXME: bit0 is listed as reserved in SCSI-2, but is
+	 * significant in SCSI-3.  For now, we follow the SCSI-2
+	 * behaviour and ignore reserved bits. */
+	
+	status &= 0xfe;
+
+	return ((status & SAM_STAT_GOOD)
+		|| (status & SAM_STAT_INTERMEDIATE)
+		|| (status & SAM_STAT_INTERMEDIATE_CONDITION_MET)
+		/* FIXME: this is obsolete in SAM-3 */
+		|| (status & SAM_STAT_COMMAND_TERMINATED));
+}
+
 /*
  *  Status codes. These are deprecated as they are shifted 1 bit right
  *  from those found in the SCSI standards. This causes confusion for