btrfs-progs: btrfstune: fix documentation for --enable-simple-quota

The documentation lists -q as the flag for enabling simple quotas, but
the actual parsing only handles --enable-simple-quota. Update the
documentation string.

Reviewed-by: Anand Jain <anand.jain@oracle.com>
Reviewed-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: Boris Burkov <boris@bur.io>
[ Add man page entry for `--enable-simple-quota` option ]
Signed-off-by: Qu Wenruo <wqu@suse.com>

Author: boryas

Documentation/btrfstune.rst

@@ -42,6 +42,13 @@ OPTIONS
 
         Convert to free-space-tree feature (v2 of space cache).
 
+--enable-simple-quota
+	(since kernel 6.7)
+
+	Enable simple quota accounting (*squota* mkfs feature). This is an
+	alternative to qgroups with a smaller performance impact but no notion
+	of shared vs. exclusive usage.
+
 -f
         Allow dangerous changes, e.g. clear the seeding flag or change fsid.
         Make sure that you are aware of the dangers.

tune/main.c

@@ -103,7 +103,7 @@ static const char * const tune_usage[] = {
 	OPTLINE("-x", "enable skinny metadata extent refs (mkfs: skinny-metadata)"),
 	OPTLINE("-n", "enable no-holes feature (mkfs: no-holes, more efficient sparse file representation)"),
 	OPTLINE("-S <0|1>", "set/unset seeding status of a device"),
-	OPTLINE("-q", "enable simple quotas on the file system. (mkfs: squota)"),
+	OPTLINE("--enable-simple-quota", "enable simple quotas on the file system. (mkfs: squota)"),
 	OPTLINE("--convert-to-block-group-tree", "convert filesystem to track block groups in "
 			"the separate block-group-tree instead of extent tree (sets the incompat bit)"),
 	OPTLINE("--convert-from-block-group-tree",