ocfs2: reserve inline space for extended attribute

Add the structures and helper functions we want for handling inline extended
attributes. We also update the inline-data handlers so that they properly
function in the event that we have both inline data and inline attributes
sharing an inode block.

Signed-off-by: Tiger Yang <tiger.yang@oracle.com>
Signed-off-by: Mark Fasheh <mfasheh@suse.com>