AArch64 backend: Use array parameters consistently

Currently we are using a mix of arrays and pointers:

```c
void mld_polyvecl_pointwise_acc_montgomery_l4_asm(int32_t *r,
                                                  const int32_t a[4][MLDSA_N],
                                                  const int32_t b[4][MLDSA_N])Collapse comment
```

This should be unified to use arrays consistently. 