MFC r295276: Add defines for WRITE_UNCORRECTABLE ATA command, and improve
command logging

Add #defines for ATA_WRITE_UNCORRECTABLE48 and its features. Update the
decoding in ATACAM to recognize the new values. Also improve command
decoding for a few other commands (SMART, NOP, SET_FEATURES). Bring the
decoding in ata(4) up to parity with ATACAM.

Sponsored by: Panasas, Inc.