ocfs2: fix function declaration and definition in xattr

Because we merged the xattr sources into one file, some functions
no longer belong in the header file.

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