floppy: add references to 82077's extra registers

This controller provides extra status registers SRA and SRB as well
as a tape drive register (TDR) and a data rate select register (DSR),
which are referenced in the sparc port, so let's have their symbolic
definitions centralized.

Link: https://lore.kernel.org/r/20200331094054.24441-3-w@1wt.euSigned-off-by: Willy Tarreau <w@1wt.eu>
Signed-off-by: Denis Efremov <efremov@linux.com>

include/uapi/linux/fdreg.h

@@ -7,13 +7,23 @@
  * Handbook", Sanches and Canton.
  */
 
-/* Fd controller regs. S&C, about page 340 */
-#define FD_STATUS	4
-#define FD_DATA		5
+/* 82077's auxiliary status registers A & B (R) */
+#define FD_SRA		0
+#define FD_SRB		1
 
 /* Digital Output Register */
 #define FD_DOR		2
 
+/* 82077's tape drive register (R/W) */
+#define FD_TDR		3
+
+/* 82077's data rate select register (W) */
+#define FD_DSR		4
+
+/* Fd controller regs. S&C, about page 340 */
+#define FD_STATUS	4
+#define FD_DATA		5
+
 /* Digital Input Register (read) */
 #define FD_DIR		7