nvme: Add OAES bit-field definitions

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);

(cherry picked from commit e71afa1202750b7cc8d49e77b7eed0114ece1657)