lightnvm: rename per bio data structs

Shorting the naming to make lines shorter.
lightnvm: remove inclues from .c files

We make all the includes within the lightnvm header file.
lightnvm: code style cleanup
lightnvm: nvm_update_map can no longer fail

Remove the logic that handled in nvm_update_map failed. As we now track
inflight IOs and only allow a single at a time, we can simplify a lot of
the logic around failures during GC (as they don't happen anymore)
lightnvm: make core.c follow linux style fully
lightnvm: make reg.c follow code style
lightnvm: fix up gc.c for style errors