common/xfs: fix _scratch_mkfs_xfs_supports_concurrency

generic/347 regresses when external logs are in the configuration:

 --- a/generic/347.out		2025-07-15 14:45:15.044714644 -0700
 +++ b/generic/347.out.bad	2026-05-18 23:17:01.687750781 -0700
 @@ -1,2 +1,36 @@
  QA output created by 347
 -=== completed
 +Cannot specify both -l logdev and -l concurrency
 +Usage: mkfs.xfs

Since this actually tests running mkfs.xfs with $SCRATCH_OPTIONS, the
helper ought to have detected that you can't give both.  Unfortunately,
there's a weird switch that turns -l into -d even though they're not
quite the same option.  Delete that, and fix the indentation (tabs, not
spaces) in the helper.

Cc: fstests@vger.kernel.org # v2026.05.17
Fixes: 7f162f5bcf50fc ("common/xfs: helper function to check if -l/-d/-r concurrecy flags.")
Signed-off-by: "Darrick J. Wong" <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Zorro Lang <zlang@kernel.org>