mbuf: minor changes for readability
mbuf: minor changes for readability

* Ensure comments line up correctly
* Simplify the #ifdefs around the refcnt fields to make them clearer

Signed-off-by: Bruce Richardson <66b9e8e8fbd5e9f41f91b0af050876182ce9d0e4@intel.com>
Acked-by: Olivier Matz <dfcc1510895413197abb4336e39bb0a3906cba71@6wind.com>

tsphillips/dpdk-fork,venkynv/dpdk-mirror,venkynv/dpdk-mirror,mixja/dpdk,msune/dpdk,msune/dpdk,john-mcnamara-intel/dpdk,venkynv/dpdk-mirror,venkynv/dpdk-mirror,john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk,msune/dpdk,mixja/dpdk,mixja/dpdk,tsphillips/dpdk-fork,mixja/dpdk,john-mcnamara-intel/dpdk,tsphillips/dpdk-fork,tsphillips/dpdk-fork,msune/dpdk