openrisc: sanitize use of orig_gpr11

The pt_regs struct had both a 'syscallno' field and an 'orig_gpr11' field
and it wasn't really clear how these were supposed to be used.  This patch
removes the syscallno field altogether and makes orig_gpr11 work more
like other architectures: keep track of syscall number in progress or
hold -1 for non-syscall exceptions.

Signed-off-by: Jonas Bonn <jonas@southpole.se>

arch/openrisc/include/asm/ptrace.h

@@ -73,9 +73,13 @@ struct pt_regs {
 		};
 	};
 	long  pc;
+	/* For restarting system calls:
+	 * Set to syscall number for syscall exceptions,
+	 * -1 for all other exceptions.
+	 */
 	long  orig_gpr11;	/* For restarting system calls */
-	long  syscallno;	/* Syscall number (used by strace) */
 	long dummy;		/* Cheap alignment fix */
+	long dummy2;		/* Cheap alignment fix */
 };
 
 /* TODO: Rename this to REDZONE because that's what it is */