The shared radix-tree build is not correctly recompiling when
lib/maple_tree.c and lib/test_maple_tree.c are modified - fix this by
adding these core components to the SHARED_DEPS list.

Additionally, add missing header guards to shared header files.

Link: https://lkml.kernel.org/r/20240924180724.112169-1-lorenzo.stoakes@oracle.com
Fixes: 74579d8d ("tools: separate out shared radix-tree components")
Signed-off-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Tested-by: Sidhartha Kumar <sidhartha.kumar@oracle.com>
Cc: "Liam R. Howlett" <Liam.Howlett@oracle.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>