xfs: move xfs_xattr_handlers to .rodata

This makes it harder for accidental or malicious changes to
xfs_xattr_handlers at runtime.

Cc: "Darrick J. Wong" <djwong@kernel.org>
Cc: linux-xfs@vger.kernel.org
Signed-off-by: Wedson Almeida Filho <walmeida@microsoft.com>
Link: https://lore.kernel.org/r/20230930050033.41174-27-wedsonaf@gmail.com


Reviewed-by: "Darrick J. Wong" <djwong@kernel.org>
Signed-off-by: Christian Brauner <brauner@kernel.org>