Convert ioctl helper functions to macros

[MaisenbacherD]

We need to keep the core ioctl.h functions (the functions that are not static inline).
Convert the ioctl helper functions into nvme_passthru_cmd initializer setter macros. These macros should then be called from the user before issuing the core function.

As discussed with the community at ALPSS

[igaw]

nvme-experiments#54