hw/scsi: Fix debug message of cdb structure in scsi-generic

When running with debug enabled, the scsi-generic cdb that is
dumped skips byte 0 of the command, which is the opcode.  This
makes identifying which command is being issued/completed a
little difficult.  Example:

  0x00 0x00 0x01 0x00 0x00
  scsi-generic: scsi_read_data 0x0
  scsi-generic: Data ready tag=0x0 len=164
  scsi-generic: scsi_read_data 0x0
  scsi-generic: Command complete 0x0x10a42c60 tag=0x0 status=0

Improve this by adding a message prior to the loop, similar to
what exists for scsi-disk.  Clean up a few other messages to be
more explicit of what is being represented.  Example:

  scsi-generic: Command: data=0x12 0x00 0x00 0x01 0x00 0x00
  scsi-generic: scsi_read_data tag=0x0
  scsi-generic: Data ready tag=0x0 len=164
  scsi-generic: scsi_read_data tag=0x0
  scsi-generic: Command complete 0x0x10a452d0 tag=0x0 status=0
Signed-off-by: NEric Farman <farman@linux.vnet.ibm.com>
Message-Id: <20170120162527.66075-2-farman@linux.vnet.ibm.com>
Reviewed-by: NFam Zheng <famz@redhat.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

hw/scsi/scsi-generic.c

@@ -246,7 +246,7 @@ static void scsi_read_data(SCSIRequest *req)
     SCSIDevice *s = r->req.dev;
     int ret;
 
-    DPRINTF("scsi_read_data 0x%x\n", req->tag);
+    DPRINTF("scsi_read_data tag=0x%x\n", req->tag);
 
     /* The request is used as the AIO opaque value, so add a ref.  */
     scsi_req_ref(&r->req);
@@ -294,7 +294,7 @@ static void scsi_write_data(SCSIRequest *req)
     SCSIDevice *s = r->req.dev;
     int ret;
 
-    DPRINTF("scsi_write_data 0x%x\n", req->tag);
+    DPRINTF("scsi_write_data tag=0x%x\n", req->tag);
     if (r->len == 0) {
         r->len = r->buflen;
         scsi_req_data(&r->req, r->len);
@@ -329,6 +329,7 @@ static int32_t scsi_send_command(SCSIRequest *req, uint8_t *cmd)
     int ret;
 
 #ifdef DEBUG_SCSI
+    DPRINTF("Command: data=0x%02x", cmd[0]);
     {
         int i;
         for (i = 1; i < r->req.cmd.len; i++) {