This cleans up the I/O splitting code somewhat.
It also moves the SGL payload function pointers up into the hot cache
section of struct nvme_request without pushing the other important
members past the cacheline boundary (because payload is now a union).
Change-Id: I14a5c24f579d57bb84d845147d03aa53bb4bb209
Signed-off-by: Daniel Verkamp <daniel.verkamp@intel.com>
407a57165d