LU-17576 nodemap: remove nodemap_rbtree.c

LU-17576 nodemap: remove nodemap_rbtree.c

Remove nodemap_rbtree.c. This was a port of an
in-progress rbtree patch to the kernel. Every
kernel that Lustre supports should have the needed
macro. The rest of the stuff in the file is unused.

Signed-off-by: Timothy Day <timday@amazon.com>
Change-Id: I25d6eea90a1e9b983fb0be690384e50c6808cb7b
Reviewed-on: https://review.whamcloud.com/c/fs/lustre-release/+/54136
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: Sebastien Buisson <sbuisson@ddn.com>
Reviewed-by: James Simmons <jsimmons@infradead.org>