ide-floppy: ->{srfp,wp} -> IDE_AFLAG_{SRFP,WP}

Add IDE_AFLAG_{SRFP,WP} drive->atapi_flags and use them
instead of ->{srfp,wp} struct ide_floppy_obj fields.

There should be no functional changes caused by this patch.

Acked-by: Borislav Petkov <petkovbb@gmail.com>
Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>