[PATCH] libata: cosmetic changes in ata_bus_softreset()

ata_bus_softreset() should return AC_ERR_* on failure not arbitrary
positive number.  While at it, reformat comment above it.

Signed-off-by: Tejun Heo <htejun@gmail.com>
Acked-by: Alan Cox <alan@redhat.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>