isci: uplevel request infrastructure

* Consolidate tiny header files
* Move files out of core/ (drop core/scic_sds_ prefix)
* Merge core/scic_sds_request.[ch] into request.[ch]
* Cleanup request.c namespace (clean forward declarations and global
  namespace pollution)

Reported-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

drivers/scsi/isci/Makefile

@@ -7,11 +7,9 @@ isci-objs := init.o phy.o request.o sata.o \
 	     remote_node_context.o \
 	     remote_node_table.o \
 	     unsolicited_frame_control.o \
-	     core/scic_sds_request.o \
-	     core/scic_sds_stp_request.o \
+	     stp_request.o \
+	     ssp_request.o \
+	     smp_request.o \
 	     core/scic_sds_port.o \
 	     core/scic_sds_port_configuration_agent.o \
 	     core/scic_sds_phy.o \
-	     core/scic_sds_ssp_request.o \
-	     core/scic_sds_smp_request.o \
-	     core/sci_util.o