mkfs: fix the issue of maxpct set to 0 not taking effect

mkfs: fix the issue of maxpct set to 0 not taking effect

If a filesystem has the sb_imax_pct field set to zero, there is no limit to the number of inode blocks in the filesystem.

However, when using mkfs.xfs and specifying maxpct = 0, the result is not as expected.
	[root@fs ~]# mkfs.xfs -f -i maxpct=0 xfs.img
	data     =               bsize=4096   blocks=262144, imaxpct=25
	         =               sunit=0      swidth=0 blks

The reason is that the condition will never succeed when specifying maxpct = 0. As a result, the default algorithm was applied.
	cfg->imaxpct = cli->imaxpct;
	if (cfg->imaxpct)
		return;

The result with patch:
	[root@fs ~]# mkfs.xfs -f -i maxpct=0 xfs.img
	data     =               bsize=4096   blocks=262144, imaxpct=0
	         =               sunit=0      swidth=0 blks

	[root@fs ~]# mkfs.xfs -f xfs.img
	data     =               bsize=4096   blocks=262144, imaxpct=25
	         =               sunit=0      swidth=0 blks

Cc: linux-xfs@vger.kernel.org # v4.15.0
Fixes: d7240c965389e1 ("mkfs: rework imaxpct calculation")
Suggested-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: liuh <liuhuan01@kylinos.cn>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>