ext4: fix build error when DX_DEBUG is defined

ext4: fix build error when DX_DEBUG is defined

Enabling DX_DEBUG triggers the build error below.  info is an attribute
of  the dxroot structure.

linux/fs/ext4/namei.c:2264:12: error: ‘info’
undeclared (first use in this function); did you mean ‘insl’?
	   	  info->indirect_levels));

Fixes: 78556404e810 ("ext4: add largedir feature")
Signed-off-by: Gabriel Krisman Bertazi <krisman@collabora.co.uk>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Reviewed-by: Lukas Czerner <lczerner@redhat.com>