ata: libata: avoid kernel-doc warnings

ata: libata: avoid kernel-doc warnings

Modify comments to prevent kernel-doc warnings:
- use "/*" for a non-kernel-doc comment
- add a Returns: section for ata_id_major_version()

Warning: include/linux/ata.h:770 Cannot find identifier on line:
 *
Warning: include/linux/ata.h:782 function parameter 'id' not described in 'ata_id_sct_data_tables'
Warning: include/linux/ata.h:782 expecting prototype for Word(). Prototype was for ata_id_sct_data_tables() instead
Warning: include/linux/ata.h:820 No description found for return value of 'ata_id_major_version'

Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Damien Le Moal <dlemoal@kernel.org>