nvme: Add OAES bit-field definitions

[chuck]

Summary

Create definitions for the Optional Asynchronous Events Supported (OAES)
values. Also adds a helper macro for the common use case of "mask and
shift". E.g.

value = NVME_CTRLR_DATA_OAES_NS_ATTR_MASK << NVME_CTRLR_DATA_OAES_NS_ATTR_SHIFT;

becomes

value = NVMEB(NVME_CTRLR_DATA_OAES_NS_ATTR);

[chuck]

The new OAES defines are probably fine, but I'd like some feedback on the NVMEB() helper macro. Do you like it? Hate it? Have a better approach? Better name?

[mav]

Looks good to me, I just think we could add more while there.

sys/dev/nvme/nvme.h

257

Where is the mask for the bit 14? Looking on NVMe 2.0 spec I see few more bits here. Why not add them too?

[chuck]

Added missing mask for Endurance Group (bit 14) and added new
definitions from the 2.0 specification