misc: fix reversed calloc arguments

misc: fix reversed calloc arguments

gcc 14 complains about reversed arguments to calloc:

namei.c: In function ‘path_parse’:
namei.c:51:32: warning: ‘calloc’ sizes specified with ‘sizeof’ in the earlier argument and not in the later argument [-Wcalloc-transposed-args]
   51 |         dirpath = calloc(sizeof(*dirpath), 1);
      |                                ^
namei.c:51:32: note: earlier argument should specify number of elements, later size of each element

Fix all of these.

Signed-off-by: "Darrick J. Wong" <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>