cpukit/libfs/src/rfs/*: Address unused parameter warnings

Add "(void) param;" annotation to address unused parameter warnings.
Found with GCC's warning -Wunused-paramter.

cpukit/libfs/src/rfs/rtems-rfs-rtems-dev.c

@@ -195,6 +195,9 @@ rtems_rfs_rtems_device_ioctl (rtems_libio_t*  iop,
 static int
 rtems_rfs_rtems_device_ftruncate (rtems_libio_t* iop, off_t length)
 {
+  (void) iop;
+  (void) length;
+
   return 0;
 }
 

cpukit/libfs/src/rfs/rtems-rfs-rtems-dir.c

@@ -60,6 +60,10 @@ rtems_rfs_rtems_dir_open (rtems_libio_t* iop,
                           int            oflag,
                           mode_t         mode)
 {
+  (void) pathname;
+  (void) oflag;
+  (void) mode;
+
   rtems_rfs_file_system* fs = rtems_rfs_rtems_pathloc_dev (&iop->pathinfo);
   rtems_rfs_ino          ino = rtems_rfs_rtems_get_iop_ino (iop);
   rtems_rfs_inode_handle inode;
@@ -98,6 +102,8 @@ rtems_rfs_rtems_dir_open (rtems_libio_t* iop,
 static int
 rtems_rfs_rtems_dir_close (rtems_libio_t* iop)
 {
+  (void) iop;
+
   /*
    * The RFS does not hold any resources. Nothing to do.
    */

cpukit/libfs/src/rfs/rtems-rfs-rtems-file.c

@@ -58,6 +58,8 @@ rtems_rfs_rtems_file_open (rtems_libio_t* iop,
                            int            oflag,
                            mode_t         mode)
 {
+  (void) oflag;
+
   rtems_rfs_file_system* fs = rtems_rfs_rtems_pathloc_dev (&iop->pathinfo);
   rtems_rfs_ino          ino;
   rtems_rfs_file_handle* file;

cpukit/libfs/src/rfs/rtems-rfs-rtems.c

@@ -92,6 +92,8 @@ rtems_rfs_rtems_is_directory(
   void *arg
 )
 {
+  (void) ctx;
+
   rtems_rfs_inode_handle* inode = arg;
 
   return S_ISDIR (rtems_rfs_inode_get_mode (inode));

cpukit/libfs/src/rfs/rtems-rfs-shell.c

@@ -137,6 +137,9 @@ rtems_rfs_get_fs (const char* path, rtems_rfs_file_system** fs)
 static int
 rtems_rfs_shell_data (rtems_rfs_file_system* fs, int argc, char *argv[])
 {
+  (void) argc;
+  (void) argv;
+
   size_t blocks;
   size_t inodes;
   int    bpcent;