The kernel_2x2 function uses 4 ZA tiles (0-3) each with svl slices.
Tiles 0/1 handle rows 0..svl-1 with slice indices 0..svl-1.
Tiles 2/3 handle rows svl..2*svl-1, so their slice indices
must start at 0, i.e. (i - svl) instead of i.
Fix all three tile 2/3 access sites:
- C load into ZA (svwrite_hor_za32_f32_m)
- C writeback for UPPER (svst1_hor_za32)
- C writeback for LOWER (svst1_hor_za32)
Fixes#5873
Julien Schueller
43f0a90e1b