commit 33c1002e incorrectly changed return
value from '0' to '-1', fix it (ns87415 was the only host driver affected
since it uses both IDE_HFLAG_TRUST_BIOS_FOR_DMA and IDE_HFLAG_NO_ATAPI_DMA).
Signed-off-by: NBartlomiej Zolnierkiewicz <bzolnier@gmail.com>