isci: cleanup tag macros

A tag is a 16 bit number where the upper four bits is a sequence number
and the remainder is the task context index (tci).  Sanitize the macro
names and shave 256-bytes out of scic_sds_controller by reducing the size of
io_request_sequence.

scic_sds_io_tag_construct --> ISCI_TAG
scic_sds_io_tag_get_sequence --> ISCI_TAG_SEQ
scic_sds_io_tag_get_index() --> ISCI_TAG_TCI
scic_sds_io_sequence_increment() [delete / open code]

Signed-off-by: Dan Williams <dan.j.williams@intel.com>
diff --git a/drivers/scsi/isci/isci.h b/drivers/scsi/isci/isci.h
index 84ba533..81bade4 100644
--- a/drivers/scsi/isci/isci.h
+++ b/drivers/scsi/isci/isci.h
@@ -83,6 +83,7 @@
 #define SCI_MAX_SMP_PHYS  (384) /* not silicon constrained */
 #define SCI_MAX_REMOTE_DEVICES (256UL)
 #define SCI_MAX_IO_REQUESTS (256UL)
+#define SCI_MAX_SEQ (16)
 #define SCI_MAX_MSIX_MESSAGES  (2)
 #define SCI_MAX_SCATTER_GATHER_ELEMENTS 130 /* not silicon constrained */
 #define SCI_MAX_CONTROLLERS 2
@@ -113,6 +114,7 @@
 	BUILD_BUG_ON_NOT_POWER_OF_2(SCU_MAX_COMPLETION_QUEUE_ENTRIES);
 	BUILD_BUG_ON(SCU_MAX_UNSOLICITED_FRAMES > SCU_ABSOLUTE_MAX_UNSOLICITED_FRAMES);
 	BUILD_BUG_ON_NOT_POWER_OF_2(SCI_MAX_IO_REQUESTS);
+	BUILD_BUG_ON_NOT_POWER_OF_2(SCI_MAX_SEQ);
 }
 
 /**