xfs_io: fix gcc complaints about potentially uninitialized variables

xfs_io: fix gcc complaints about potentially uninitialized variables

When I turned on UBSAN on the userspace build with gcc 12.2, I get this:

bulkstat.c: In function ‘bulkstat_single_f’:
bulkstat.c:316:24: error: ‘ino’ may be used uninitialized [-Werror=maybe-uninitialized]
  316 |                 ret = -xfrog_bulkstat_single(&xfd, ino, flags, &bulkstat);
      |                        ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
bulkstat.c:293:41: note: ‘ino’ was declared here
  293 |                 uint64_t                ino;
      |                                         ^~~

I /think/ this is a failure of the gcc static checker to notice that sm
will always be set to the last element of the tags[] array if it didn't
set ino, but this code could be more explicit about deciding to
fallback to strtoul.

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