LU-12481 osd-ldiskfs: allow full 64KB xattr size

LU-12481 osd-ldiskfs: allow full 64KB xattr size

When the 'ea_inode' feature is enabled, allow the full 64KB xattr
size, since the xattr data is stored directly in the ea_inode data
blocks, while the ext4_xattr_entry and ext4_xattr_hdr structures are
stored separately in the parent inode or external xattr block.

This avoids errors on the client trying to set a full-sized inode:

    setfattr: /mnt/lustre/f61.conf-sanity: Argument list too long

Fixes: 3ec712bd183a ("LU-11868 osd: Set max ea size to XATTR_SIZE_MAX")
Signed-off-by: Andreas Dilger <adilger@whamcloud.com>
Change-Id: I1320c32af98ab0feeeb147d8dbbc66ec7d1b8e1f
Reviewed-on: https://review.whamcloud.com/35352
Tested-by: jenkins <devops@whamcloud.com>
Reviewed-by: Patrick Farrell <pfarrell@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Wang Shilong <wshilong@ddn.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>