LU-6757 ldiskfs: large EA support

LU-6757 ldiskfs: large EA support

For large EA support, ext4_xattr_check_names() will return -EIO. This
patch fixes that by checking whether the large EA value is saved in an
external EA inode or not.

this mod copys a small subset of http://review.whamcloud.com/16012 that made
this change in el7 ldiskfs into sles12 ldiskfs

Signed-off-by: Bob Glossman <bob.glossman@intel.com>
Change-Id: I5f29eb5d87e1a3a0a928298ed3ac993c7a0bcdd1
Reviewed-on: http://review.whamcloud.com/18449
Tested-by: Jenkins
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Jian Yu <jian.yu@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>