Remove dead *_MOK MPI-offset assignments in file_per_process I/O branches (and fix n_MOK/p_MOK typo) #1490

In the sequential file_per_process restart I/O paths, the *_MOK MPI byte-offset variables are computed but never consumed: these branches open with MPI_COMM_SELF and read/write sequentially via MPI_FILE_READ / MPI_FILE_WRITE_ALL with no MPI_FILE_SET_VIEW and no disp displacement. The offsets are only meaningful in the other (collective, set-view) path, which recomputes them itself.

1. src/simulation/m_start_up.fpp:403-407 (read path, inside if (file_per_process) opened with MPI_COMM_SELF):

m_MOK = int(m_glb_read + 1, MPI_OFFSET_KIND)
n_MOK = int(m_glb_read + 1, MPI_OFFSET_KIND)   ! BUG: uses m_glb_read
p_MOK = int(m_glb_read + 1, MPI_OFFSET_KIND)   ! BUG: uses m_glb_read
WP_MOK = int(storage_size(0._stp)/8, MPI_OFFSET_KIND)
MOK = int(1._wp, MPI_OFFSET_KIND)

Two issues:

• Dead: none of m_MOK/n_MOK/p_MOK/WP_MOK/MOK/var_MOK are read in this branch — the reads are plain sequential MPI_FILE_READ with no SET_VIEW/disp.
• Copy-paste typo: n_MOK and p_MOK are both derived from m_glb_read instead of n_glb_read / p_glb_read (computed just above). Latent (harmless only because unused), but a real bug that would surface if SET_VIEW were ever wired into this path.

2. src/simulation/m_data_output.fpp:718-724 (write path, inside MPI_COMM_SELF):

m_MOK = int(m_glb_save + 1, MPI_OFFSET_KIND)
n_MOK = int(n_glb_save + 1, MPI_OFFSET_KIND)
p_MOK = int(p_glb_save + 1, MPI_OFFSET_KIND)
WP_MOK = int(storage_size(0._stp)/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)

Dead in this branch (writes are MPI_FILE_WRITE_ALL with no SET_VIEW). By contrast the other branch (m_data_output.fpp:775-798) does build disp = m_MOK*max(MOK,n_MOK)*max(MOK,p_MOK)*WP_MOK*(var_MOK-1) and calls MPI_FILE_SET_VIEW — so the variables are genuinely needed only there. No typo in this block.

Fix.

• m_start_up.fpp: delete lines 403-407 (the dead *_MOK assignments). If kept defensively, at minimum fix the typo (n_MOK ← n_glb_read, p_MOK ← p_glb_read). Recommended: delete.
• m_data_output.fpp: delete lines 718-724.
• Optionally drop the per-iteration var_MOK = int(i, ...) lines in these branches too (unused there).

Output-neutrality: removing dead assignments to never-read variables does not change file contents or behavior; the collective path that actually uses *_MOK is untouched.

_{Filed from a repo-wide code-cleanliness review; verified against master @ 40dde5e.}

Code references

• src/simulation/m_start_up.fpp:403-407 — dead *_MOK + n/p typo
• src/simulation/m_data_output.fpp:718-724 — dead *_MOK (write)
• src/simulation/m_data_output.fpp:775-798 — SET_VIEW path that uses *_MOK