sim: syscall: unify memory helpers

Almost every port implements these two callbacks in the same way, so
unify them in the common layer.

sim/common/sim-syscall.h

@@ -0,0 +1,30 @@
+/* Simulator system call support.
+
+   Copyright 2002-2015 Free Software Foundation, Inc.
+
+   This file is part of simulators.
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
+
+#ifndef SIM_SYSCALL_H
+#define SIM_SYSCALL_H
+
+/* Simple memory callbacks for cb_syscall's read_mem/write_mem that assume
+   cb_syscall's p1 and p2 are set to the SIM_DESC and SIM_CPU respectively.  */
+int sim_syscall_read_mem (host_callback *, struct cb_syscall *, unsigned long,
+			  char *, int);
+int sim_syscall_write_mem (host_callback *, struct cb_syscall *, unsigned long,
+			   const char *, int);
+
+#endif