remote-sim: Add missing ATTRIBUTE_PRINTF

remote-sim: Add missing ATTRIBUTE_PRINTF

Fixes:

/home/emaisin/src/binutils-gdb/gdb/remote-sim.c:385:34: error: format string is not a string literal [-Werror,-Wformat-nonliteral]
  vfprintf_filtered (gdb_stdout, format, args);
                                 ^~~~~~
/home/emaisin/src/binutils-gdb/gdb/remote-sim.c:394:34: error: format string is not a string literal [-Werror,-Wformat-nonliteral]
  vfprintf_filtered (gdb_stdout, format, ap);
                                 ^~~~~~
/home/emaisin/src/binutils-gdb/gdb/remote-sim.c:402:34: error: format string is not a string literal [-Werror,-Wformat-nonliteral]
  vfprintf_filtered (gdb_stderr, format, ap);
                                 ^~~~~~
/home/emaisin/src/binutils-gdb/gdb/remote-sim.c:413:11: error: format string is not a string literal [-Werror,-Wformat-nonliteral]
  verror (format, args);
          ^~~~~~
4 errors generated.

gdb/ChangeLog:

	* remote-sim.c (gdb_os_printf_filtered, gdb_os_vprintf_filtered,
	gdb_os_evprintf_filtered, gdb_os_error): Add ATTRIBUTE_PRINTF.