libfs: Always use geteuid() and getegid()

The two functions are independent of the POSIX API.

cpukit/libfs/src/imfs/imfs_creat.c

@@ -66,13 +66,8 @@ IMFS_jnode_t *IMFS_allocate_node(
    *  Fill in the mode and permission information for the jnode structure.
    */
   node->st_mode = mode;
-  #if defined(RTEMS_POSIX_API)
-    node->st_uid = geteuid();
-    node->st_gid = getegid();
-  #else
-    node->st_uid = 0;
-    node->st_gid = 0;
-  #endif
+  node->st_uid = geteuid();
+  node->st_gid = getegid();
 
   /*
    *  Now set all the times.

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

@@ -609,13 +609,8 @@ rtems_rfs_rtems_mknod (const rtems_filesystem_location_info_t *parentloc,
   gid_t                   gid;
   int                     rc;
 
-#if defined(RTEMS_POSIX_API)
   uid = geteuid ();
   gid = getegid ();
-#else
-  uid = 0;
-  gid = 0;
-#endif
 
   rc = rtems_rfs_inode_create (fs, parent, name, namelen,
                                rtems_rfs_rtems_imode (mode),