block/blkio: Make s->mem_region_alignment be 64 bits

With GCC 14 the code failed to compile on i686 (and was wrong for any
version of GCC):

../block/blkio.c: In function ‘blkio_file_open’:
../block/blkio.c:857:28: error: passing argument 3 of ‘blkio_get_uint64’ from incompatible pointer type [-Wincompatible-pointer-types]
  857 |                            &s->mem_region_alignment);
      |                            ^~~~~~~~~~~~~~~~~~~~~~~~
      |                            |
      |                            size_t * {aka unsigned int *}
In file included from ../block/blkio.c:12:
/usr/include/blkio.h:49:67: note: expected ‘uint64_t *’ {aka ‘long long unsigned int *’} but argument is of type ‘size_t *’ {aka ‘unsigned int *’}
   49 | int blkio_get_uint64(struct blkio *b, const char *name, uint64_t *value);
      |                                                         ~~~~~~~~~~^~~~~

Signed-off-by: Richard W.M. Jones <rjones@redhat.com>
Message-id: 20240130122006.2977938-1-rjones@redhat.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>

block/blkio.c

@@ -68,7 +68,7 @@ typedef struct {
     CoQueue bounce_available;
 
     /* The value of the "mem-region-alignment" property */
-    size_t mem_region_alignment;
+    uint64_t mem_region_alignment;
 
     /* Can we skip adding/deleting blkio_mem_regions? */
     bool needs_mem_regions;