libc: memfd_create should create /tmp/memfd/ before creating file

Signed-off-by: Xiang Xiao <xiaoxiang@xiaomi.com>

libs/libc/misc/lib_memfd.c

@@ -23,6 +23,7 @@
  ****************************************************************************/
 
 #include <sys/mman.h>
+#include <sys/stat.h>
 #include <errno.h>
 #include <fcntl.h>
 #include <stdio.h>
@@ -56,6 +57,7 @@ int memfd_create(FAR const char *name, unsigned int flags)
 #  ifdef CONFIG_LIBC_MEMFD_SHMFS
   return shm_open(path, O_RDWR | flags, 0660);
 #  else
+  mkdir(LIBC_MEM_FD_VFS_PATH, 0666);
   return open(path, O_RDWR | flags, 0660);
 #  endif
 #endif