MISRA rules (see #11425) forbid recursive algorithms. In the case of
rb_walk(), it's not actually used anywhere but a test right now, so we
can simply disable the API when CONFIG_MISRA_SANE is defined. Mempool
had a (IMHO, fairly clever) tail recursive loop in bfree_recombine()
which can be trivially transformed into an only slightly uglier
iterative version.
Signed-off-by: Andy Ross <andrew.j.ross@intel.com>