shmoverride: fix parameters order

GCC 14 complains:

    shmoverride.c: In function ...mmap_mfns...:
    shmoverride.c:96:30: error: ...calloc... sizes specified with ...sizeof... in the earlier argument and not in the later argument [-Werror=calloc-transposed-args]
       96 |     pfntable = calloc(sizeof(xen_pfn_t), shm_args_mfns->count);
          |                              ^~~~~~~~~
    shmoverride.c:96:30: note: earlier argument should specify number of elements, later size of each element
    cc1: all warnings being treated as errors

QubesOS/qubes-issues#8915

shmoverride/shmoverride.c

@@ -93,7 +93,7 @@ static uint8_t *mmap_mfns(struct shm_args_hdr *shm_args) {
     struct shm_args_mfns *shm_args_mfns = (struct shm_args_mfns *) (
             ((uint8_t *) shm_args) + sizeof(struct shm_args_hdr));
 
-    pfntable = calloc(sizeof(xen_pfn_t), shm_args_mfns->count);
+    pfntable = calloc(shm_args_mfns->count, sizeof(xen_pfn_t));
     if (!pfntable)
         return NULL;
     for (i = 0; i < shm_args_mfns->count; i++)