Fix residual hardcoded WP_MOK in sequential Lustre read path

The MPI_COMM_SELF read path at line 578 still used
int(4._wp, MPI_OFFSET_KIND), assuming single precision.
Apply the same storage_size fix as the rest of the PR.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: sbryngelson

src/simulation/m_start_up.fpp

@@ -575,7 +575,7 @@ contains
                 m_MOK = int(m_glb_read + 1, MPI_OFFSET_KIND)
                 n_MOK = int(m_glb_read + 1, MPI_OFFSET_KIND)
                 p_MOK = int(m_glb_read + 1, MPI_OFFSET_KIND)
-                WP_MOK = int(4._wp, MPI_OFFSET_KIND)
+                WP_MOK = int(storage_size(0._wp)/8, MPI_OFFSET_KIND)
                 MOK = int(1._wp, MPI_OFFSET_KIND)
                 str_MOK = int(name_len, MPI_OFFSET_KIND)
                 NVARS_MOK = int(sys_size, MPI_OFFSET_KIND)