libata: kill the infamous abnormal status message

The infamous abnormal status message triggers on not so abnormal cases
including empty port and even when it's being triggered on actual
errors the info it provides is redundant and out of context - higher
level functions will print the info in better safe later anyway.

Also, by being triggered all the time, it leads people to think that
the abnormality is somehow related to all ATA and system problems
they're experiencing and gives owners of healthy systems unfounded
doubts about the integrity of the universe.  Make it a DPRINTK and
save the universe.

Signed-off-by: Tejun Heo <htejun@gmail.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>