tools/testing: include maple-shim.c in maple.c

tools/testing: include maple-shim.c in maple.c

There's some duplicated code and we are about to add more functionality
in maple-shared.h that we will need in the userspace maple test to be
available, so include it via maple-shim.c

Co-developed-by: Liam R. Howlett <Liam.Howlett@oracle.com>
Signed-off-by: Liam R. Howlett <Liam.Howlett@oracle.com>
Reviewed-by: Suren Baghdasaryan <surenb@google.com>
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>